A dog growth hormone cDNA codes for a mature protein identical to pig growth hormone

Case Report: Human Recombinant Growth Hormone Therapy in a DSH Cat Presented With Dwarfism

A 6-month-old kitten, male, domestic shorthair cat was presented with dwarfism, ocular and nasal discharge, and Ascaris infestation. Congenital hyposomatotropism was diagnosed on the basis of serum level of insulin-like growth factor-1 (IGF-I). The cat was treated with human recombinant growth hormone for 9 weeks. After that, his liver enzymes became elevated, and the therapy was discontinued. His IGF-I levels were normal at the end of the therapy. Normal IGF-I was present 3 months after discontinuation of therapy with human recombinant growth hormone and even half a year after the discontinuation. All other comorbidities were addressed with the therapy. The cat is now the size of normal cats, living with the first author.

Juvenile hyposomatotropism in a Somali cat presenting with seizures due to intermittent hypoglycaemia

Case summary

A 3-month-old intact male Somali cat was evaluated for a history of seizures, hypoglycaemia and mental dullness 4 weeks after being bitten in the head by a dog. The cat’s body size and weight were approximately half that of his littermates and its haircoat was woolly, with fewer guard hairs. Multiple hypoglycaemic episodes were documented over a period of 4 weeks, which resolved rapidly after correction of the hypoglycaemia. Juvenile hyposomatotropism was presumptively diagnosed by demonstrating low circulating levels of insulin-like growth factor 1 and after exclusion of other endocrine and non-endocrine causes of small stature and hypoglycaemia. The cat’s intermittent hypoglycaemia resolved spontaneously within 1 month and the cat never showed any more neurological signs. Nevertheless, the physical retardation and the coat abnormalities remained unchanged. A year later, the cat was diagnosed with chronic kidney disease IRIS stage 2.

Relevance and novel information

Hyposomatotropism is an extremely rare feline endocrinopathy. This is the second case reported in the veterinary literature, and the only one to describe hypoglycaemic events associated with growth hormone deficiency. Although hypoglycaemia is one of the most common disease manifestations in children with pituitary dwarfism, this has not yet been reported in veterinary medicine.

Canine pancreatic islet cell tumours secreting insulin-like growth factor type 2: a rare entity

Insulin-like growth factor type II (IGF-II) is the main cause of non-islet cell tumour hypoglycaemia (NICTH) and insulin is thought to be the only factor causing hypoglycaemia in insulinomas. However, two case reports of pancreatic neuroendocrine tumours (PNETs) producing IGF-II have been previously published: a human and a canine patient. In this study, we investigated clinical, histopathological, immunohistochemical and ultrastructural features, and biological behaviour of canine pancreatic IGF-II-omas, a subgroup of PNETs that has not been previously characterized. Case records of 58 dogs with confirmed PNETs and hypoglycaemia were reviewed: six patients were affected by IGF-II-omas. Surgery was performed in all cases and two dogs had metastases. Four patients remained alive and in remission at 370, 440, 560 and 890 days post-diagnosis; two died of non-tumour-related causes. IGF-II-omas can be differentiated from insulinomas through hypoinsulinaemia, IGF-II positive and insulin negative immunostaining. The prevalence of this neoplasia is low, accounting for just 6% of PNETs.

Molecular cloning, characterization, and expression studies of water buffalo (Bubalus bubalis) somatotropin

Cloning, high-level expression, and characterization of the somatotropin (ST) gene of an indigenous Nili-Ravi breed of water buffalo Bubalus bubalis (BbST) are described. Coding, non-coding, and promoter regions of BbST were amplified and sequenced. Sequence analysis revealed several silent and two interesting point mutations on comparison with STs of other vertebrate species. One interesting variation in the BbST sequence was the replacement of a conserved glutamine residue by arginine. A plasmid was also constructed for the production of BbST in Escherichia coli BL21 (RIPL) CodonPlus, under the control of IPTG-inducible T7-lac promoter. High-level expression could be obtained by synthesizing a codon-optimized ST gene and expressing it in the form of inclusion bodies. The inclusion bodies represented over 20% of the E. coli cellular proteins. The biologically active conformation of purified BbST was confirmed by its efficient growth promoting activity in Nb2 cell proliferation assay. The expression system and purification strategy employed promise to be a useful approach to produce BbST for further use in structure-function studies and livestock industry.

Ghrelin-stimulation test in the diagnosis of canine pituitary dwarfism

This study investigated whether ghrelin, a potent releaser of growth hormone (GH) secretion, is a valuable tool in the diagnosis of canine pituitary dwarfism. The effect of intravenous administration of ghrelin on the release of GH and other adenohypophyseal hormones was investigated in German shepherd dogs with congenital combined pituitary hormone deficiency and in healthy Beagles. Analysis of the maximal increment (i.e. difference between pre- and maximal post-ghrelin plasma hormone concentration) indicated that the GH response was significantly lower in the dwarf dogs compared with the healthy dogs. In none of the pituitary dwarfs, the ghrelin-induced plasma GH concentration exceeded 5 microg/l at any time. However, this was also true for 3 healthy dogs. In all dogs, ghrelin administration did not affect the plasma concentrations of ACTH, cortisol, TSH, LH and PRL . Thus, while a ghrelin-induced plasma GH concentration above 5 microg/l excludes GH deficiency, false-negative results may occur.

Growth hormone stimulates bone healing in a critical-sized bone defect model

Growth hormone plays an important role in bone metabolism. Treating bone deficits is a major topic in orthopaedic surgery. Our hypothesis was that local continuous growth hormone administration stimulates bone healing in a canine critical-sized bone defect model. Bone formation in the defects was quantified using densitometric image analysis and histomorphometry. After growth hormone treatment, expression levels of insulin-like growth factors-I and II, and growth hormone receptor were determined in the bone regenerate of the original defects. Circulating plasma concentrations of insulin-like growth factors-I and II, and insulin- like growth factor binding proteins-4, and 6 were measured during treatment. Growth hormone administration resulted in healing of bone defects but without an additional effect of local infusion. Expression of insulin-like growth factor-I in the bone regenerate was lower in the growth hormone-treated dogs, whereas insulin-like growth factor-II and growth hormone receptor expression were not increased. Growth hormone increased circulating insulin-like growth factor-I and growth factor-II plasma concentrations. Continuous infusion of growth hormone stimulated bone healing in a canine critical-sized bone defect model. Local delivery of growth hormone did not additionally enhance bone healing. Increased circulating plasma concentrations of insulin-like growth factors-I and II most likely induced bone formation.

Production and secretion of biologically active recombinant canine growth hormone by Pichia pastoris

Production of recombinant canine (Canis familiaris) growth hormone (rCFGH) by two expression systems, methanol utilization slow (Muts) and methanol utilization plus (Mut+) based on Pichia pastoris. Led by the Saccharomyces cerevisiae alpha-mating type signal sequence (SS), the hormone was secreted into the culture medium in its mature and active form. The level of total proteins secreted into the medium achieved at 25 ml working volume using Erlenmeyer flasks was approximately 40 and 15 microg/ml for Muts and Mut+ constructs, respectively. As judged by densitometry of proteins resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the hormone produced by the fermented Mut(s) strain upon induction with methanol reached 24 microg/ml, representing around 60% of the total secreted proteins and being eight times more abundant than in its Mut+ counterpart. Finally, the recombinant hormone showed activity when tested in the Nb2 cell proliferation assay.

Different effects of physiologically and pharmacologically increased growth hormone levels on cholecalciferol metabolism at prepubertal age

The aim of the study was to investigate the influence of physiologically and pharmacologically increased plasma growth hormone (GH) levels on cholecalciferol metabolism at prepubertal age. Three groups of dogs raised on the same diet were studied from weaning till 21 weeks of age, i.e., small breed dogs (n = 7, control group); large breed dogs with 15-fold greater growth rates compared to the control group (n = 8, LB-group); and small breed dogs treated with pharmacological doses of growth hormone (n = 6, GH-group; 0.5IU GH per kg body per day) from 12 to 21 weeks of age. Excess of GH had the expected anabolic effect on growth rate and phosphate sparing. Increased plasma GH levels in the LB- and GH-groups versus the control group were accompanied by (1) greater plasma insulin-like growth factor I (IGF-I) levels, (2) greater plasma 1,25-dihydroxycholecalciferol (1,25(OH)(2)D(3)) levels, and (3) lower plasma 24,25(OH)(2)D(3) levels. In the LB-group, excess of GH favored plasma 1,25(OH)(2)D(3) levels by decreasing the clearance of 1,25(OH)(2)D(3), whereas in the GH-group by increasing the production of 1,25(OH)(2)D(3). The lowered plasma 24,25(OH)(2)D(3) levels in the LB- and GH-groups were likely attributed to a competitive inhibition of the production of 24,25(OH)(2)D(3) by GH and/or IGF-I.

Growth hormone modulates cholecalciferol metabolism with moderate effects on intestinal mineral absorption and specific effects on bone formation in growing dogs raised on balanced food

The aim of the study was to investigate the influence of growth hormone (GH) on Vitamin D3 metabolism and the subsequent effects on calcium (Ca) homeostasis and skeletal growth in growing dogs. A group of Miniature Poodles received supraphysiological doses of GH (GH group; n = 6; 0.5 IU GH per kg body per day) from 12 to 21 weeks of age and was compared with a control placebo-treated group (n = 8). Biologic activity of GH in the GH compared to the control group was indicated by (a) the 2.5- to 3.5-fold increase in the plasma concentrations of insulin-like growth factor I (IGF-I), (b) the increased production of 1,25-dihydroxycholecalciferol as indicated by the significantly increased plasma 1,25-dihydroxycholecalciferol concentrations and the 12.9-fold increase in renal 1alpha-hydroxylase gene expression, and (c) the inhibited production of 24,25-dihydroxycholecalciferol as indicated by the significantly lower plasma 24,25-dihydroxycholecalciferol concentrations and the similar levels of renal 24-hydroxylase gene expression. Despite the distinct effects on Vitamin D(3) metabolism in the GH group, there were only moderate effects on the intestine, i.e. at 20 weeks of age there was a significant increase of 14.4 and 5.6% in fractional absorption of Ca and phosphate (Pi), respectively, compared to the control group. GH administration resulted in significantly elevated glomerular filtration rate, with no differences in Pi urine excretion as a result of a concomitant increase in the tubular reabsorption of Pi. GH had only limited disturbing effects on endochondral ossification as indicated by the maintenance of the regularity of the growth plates. However, GH had specific anabolic effects on bone formation without concomitant effect on bone resorption that may result in disorders of skeletal remodeling and manifestation of enostosis.

Amino acid modifications in canine, equine and porcine pituitary growth hormones, identified by peptide-mass mapping

Modified amino acid residues in porcine, canine and equine growth hormones purified from pituitary glands were characterised by tryptic mapping and high-performance liquid chromatography with on-line coupled electrospray ionisation mass spectrometry (HPLC-ESI-MS) detection. Hormones from all three species showed the same changes. Conversion of Asp128 to iso-Asp128 was a component of native hormones, while deamidation of Asn12 and Asn98 to Asp and iso-Asp, oxidation of Met4, and cyclisation to the pyroglutamyl derivative of Gln139, probably occurred in vitro, during isolation, storage or hydrolysis. Porcine and canine hormones had indistinguishable protein fingerprints, confirming the assumption, based on their cDNA sequences, that their mature primary structures are identical.

Growth hormone induces tyrosyl phosphorylation of the transcription factors Stat5a and Stat5b in CMT-U335 canine mammary tumor cells

It has now been well documented that the normal and tumorous canine mammary glands can be extra-pituitary sites of substantial growth hormone (GH) synthesis. Until now, attempts to reproduce the GH synthesis in-vitro using canine mammary explants or mammary tumor cells have not been successful. Therefore, the response of CMT-U335 canine mammary tumor cells to administered porcine GH (pGH) was investigated as an in-vitro model to study the possible effects of GH synthesis on this site. CMT-U335 cells spontaneously express the growth hormone receptor (GHR) as well as the prolactin receptor (PRLR). Twenty five minutes after administration, GH induced, in a dose-dependent manner, phosphorylation of the transcription factors Stat5a and Stat5b. Clear phosphorylation was induced by 10(-7) M and 10(-8) M pGH, with virtually no phosphorylation at 10(-9) M pGH. A similar dose-dependent phosphorylation of Stat5a by ovine prolactin was found in these cells. Although at high concentrations binding of pGH to the canine PRLR can occur (albeit with a low pKa), the similar dose-dependent effect of oPRL on Stat5a phosphorylation indicated that pGH signaled through the GHR. Remarkably, pGH induced a moderately decreased proliferation of CMT-U335 tumor cells, which may indicate that GH induces differentiation in these tumor cells. The GH-induced activation of Stat5a and Stat5b in these cells, as part of the JAK/Stat signal transduction pathway, is consistent with mammary GH playing a role in autocrine and/or paracrine stimulation of (tumorous) mammary cells.

Morphological changes in the kidney of dogs chronically exposed to exogenous growth hormone

Porcine growth hormone was administered subcutaneously to beagle dogs at doses of 0.025, 0.1, and 1 IU/kg/d for 14 weeks, markedly elevating serum growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels. This was accompanied by a significant increase in body weight gain and kidney weights in both male and female dogs. The increase in kidney weight (6 to 54%) was slightly greater than the increase in body weight (6 to 40%). By light microscopy, glomerular deposits, mesangial thickening, and very slight cellular infiltration in glomeruli were seen in mid- and high-dose groups. Based on morphometric evaluation, there was an increase in the renal glomerular area, which was statistically significant (p < or = 0.05) in the mid- and high-dose males and in the high-dose females. This was associated with a statistically significant (p < or = 0.05) increase in the number of total glomerular cells in the mid- and high-dose males. By transmission electron microscopy, thickening of the glomerular basal lamina and diffuse increase of the mesangial matrix were observed in both male and female dogs in the mid- and high-dose groups. Immunohistochemical reactions were negative for IgG, IgM, and C3. The morphological changes in the kidney of dogs resemble the diffuse glomerulosclerosis described in human diabetic nephropathy.

Canine mammary growth hormone gene transcription initiates at the pituitary-specific start site in the absence of Pit-1

Growth hormone (GH) gene expression has been reported in the mammary glands of various mammalian species. The mechanism by which the GH gene becomes activated in extrapituitary tissues is currently unclear. We have characterized the canine mammary and pituitary GH gene transcripts by Northern blot, 5'- and 3'-RACE (rapid amplification of cDNA ends), and DNA sequence analysis. Northern blot analysis detected GH gene transcripts in mammary glands of dogs which were exposed to high levels of progestins. The mammary and pituitary GH cDNAs were shown to be identical in both the coding region and untranslated regions. Pituitary GH gene expression is highly dependent upon the transcription factor Pit-1. Analysis of Pit-1 gene expression using RT-PCR followed by Southern hybridization revealed a strong pituitary signal but faint, weak or no hybridization signals in mammary gland samples. Among the negative samples were progestin-treated dogs with high mammary GH gene expression. These findings indicate that mammary and pituitary GH gene transcripts originate from the same transcription start site but are regulated differentially.

Growth hormone and placental lactogen: biology, medicine and biotechnology

Molecular cloning gave us access to the gene members of the human growth hormone and placental lactogen multigene family. Genomic sequencing provided clues for the understanding of the origin, functioning and regulation of this family. It has also allowed us to develop new diagnostic approaches for deficiencies of these hormones and to make new biotechnological contributions.

Progestin-induced growth hormone (GH) production in the treatment of dogs with congenital GH deficiency

The recent demonstration of the ability of progestins to induce the expression of the growth hormone (GH) gene in the mammary gland of dogs and cats opens possibilities for the treatment of some forms of GH deficiency with progestins. Therefore, one male and one female German shepherd dog with congenital dwarfism because of a pituitary anomaly were treated with subcutaneous injections of medroxyprogesterone acetate (MPA) in doses of 2.5-5.0 mg per kg body weight, initially at 3-wk intervals and subsequently at 6-wk intervals. In both dogs, body sizes increased and a complete adult hair coat developed. Undesirable side-effects were recurrent periods of pruritic pyoderma in both dogs and cystic endometrial hyperplasia with mucometra in the female dog. Parallel with the physical improvements, plasma insulin-like growth factor I concentrations rose sharply. Plasma GH concentrations tended to rise, but never exceeded the upper limit of the reference range. Nevertheless, one of the dogs developed slight acromegalic features, possibly because mammary GH, unlike pituitary GH, is released evenly throughout the day. Even moderate increases in circulating GH concentration may, therefore, give rise to overexposure. It is concluded that long-term treatment with MPA can be used as an alternative for heterologous GH in the treatment of congenital GH deficiency in the dog.

Morphological changes in the pituitary gland of dogs chronically exposed to exogenous growth hormone

Growth hormone (GH) synthesis and release from the pituitary is regulated by hypothalamic releasing hormone, insulin-like growth factor-1 (IGF-1), and somatostatin. However, the potential effects of pharmacological doses of exogenous GH on the pituitary are not well studied. To determine the potential chronic effects of exogenous GH on pituitary morphology in dogs, porcine GH (pGH) was administered subcutaneously to 3 groups of dogs (4 animals/sex/group) at doses of 0.025, 0.1, and 1.0 IU/kg/day for 14 wk. A group (4/sex) of dogs served as the vehicle control. The pituitaries from all dogs were weighed and fixed in appropriate fixatives for light and electron microscopic examination; in addition, cells of the pars distalis were quantitated by a point counting method following immunostaining to identify cells containing GH, prolactin (PRL), and adrenocorticotrophic (ACTH) hormones. Administration of pGH resulted in a statistically significant (p < or = 0.05) increased pituitary weight through the high dose. By light microscopy (LM), hypertrophy of pars distalis cells was evident in mid- and high-dose female dogs. The pituitaries of dogs given the lowest dose (0.025 IU/kg/day) of pGH were not remarkable based on weight and LM findings. In addition, transmission electron microscopic (TEM) examination of the pituitary gland of high-dose demonstrated, in both sexes, pituitary cells with variably dilated rough endoplasmic reticulum and decreased numbers of secretory granules; some of these cells reacted positively to GH immunostaining. Quantitative analysis of the pituitary gland of high-dose males and females showed an increase in the absolute volume of all cell populations studied: GH-, PRL-, and ACTH-positive cells. Based on the LM and TEM findings, the increased volume of the cell populations studied is likely related to cellular hypertrophy. The expected elevation in serum GH levels following repeated administration of pGH and an associated elevation in serum IGF-1 levels resulted in morphologic changes in the pituitary gland of dogs given high doses (> or = 0.1 IU/kg/day) of pGH; these observations differed from the reported findings in pituitaries of transgenic mice secreting large quantities of bovine GH.

Effect of chronic growth hormone administration on skeletal muscle in dogs

Administration of growth hormone (GH) results in increased body weight gain in dogs. Increased body weight gain is believed to be a result of the trophic effect of GH on the musculoskeletal system. However, edema is one of the side effects described in man following exogenous GH administration. Thus, the objective of this study was to determine if the expected increased weight gain in GH-treated dogs is a result of increased muscle mass. Porcine growth hormone (pGH), administered subcutaneously to beagle dogs at doses of 0.025, 0.1, and 1 IU/kg/day for 14 wk, resulted in elevated serum GH and insulin-like growth factor-1 (IGF-1) levels (see accompanying paper, Prahalada et al). This was associated with a significant increase in body weight gain and weights of the cranial tibialis muscle in both male and female dogs. The increased muscle mass likely contributed to the significant increase in body weight gain seen in both sexes. Quantitative analysis of skeletal muscle sections stained for ATPase activity showed increases in type I (slow twitch) and type II (fast twitch) myofiber sizes in mid- and high-dose males and in high-dose females. The ratio of type I and type II muscle fibers remained unchanged. Hypertrophic myofibers were enlarged but had a normal histologic and ultrastructural organization when observed by light and transmission electron microscopy. The results of this study have demonstrated that increased muscle mass in pGH-treated dogs is related to hypertrophy of muscle fibers and not due to edema. Exogenous GH administration has an anabolic effect on skeletal muscle in dogs.

Pharmacological and toxicological effects of chronic porcine growth hormone administration in dogs

The purpose of this study was to evaluate the pharmacological and toxicological effects of exogenous GH administration in normal adult dogs. Because porcine GH (pGH) is structurally identical to canine GH, pGH was selected for a 14-wk study in dogs. Thirty-two dogs (< 2 yr) were randomized to 4 groups (4 dogs/sex/group); 1 group was treated with the vehicle and 3 groups received pGH at 0.025, 0.1, or 1.0 IU/kg/day subcutaneously. Daily clinical signs and weekly body weights were recorded. Hematology, serum biochemistry, urinalyses, electrocardiograms, and ophthalmoscopic examinations were done. Serum GH, insulin-like growth factor-1 (IGF-1), insulin, thyroxine (T4), triiodothyronine (T3), and cortisol levels were determined. Necropsies were performed, organs weighed, and tissues were fixed and processed for light microscopic examination. Porcine GH caused increased body weight gain (p < or = 0.05) through the mid dose; the mean weight gains at study termination in mid- and high-dose groups were 2.8 kg and 4.7 kg, respectively, compared to 0.4 kg and 0.8 kg in control and low-dose groups, respectively. Dose-related increased weights of liver, kidney, thyroid, pituitary gland, skeletal muscle, and adrenal gland were noted. In pGH-treated dogs, increased skin thickness seen grossly correlated histologically with increased dermal collagen. There was no gross or histomorphological evidence of edema. There were dose-related increased serum IGF-1 levels (approximately 2-10-fold; p < or = 0.05) that correlated with the elevated serum GH levels in pGH-treated dogs. Also, increased serum insulin levels (p < or = 0.05) through the mid dose were seen throughout the study. In high-dose dogs, the insulin levels remained elevated over 24 hr postdose. The serum glucose levels in fasted dogs remained within the control range and there was no chronic hyperglycemia based on glycosylated hemoglobin levels. Renal glomerular changes, significant polyuria with decreased urine specific gravity, and increased serum insulin levels suggested that the dogs had early insulin-resistant diabetes. There was minimal or no biologically significant effect of pGH on serum T3, T4, and cortisol levels in dogs. Other serum biochemical changes in pGH-treated dogs included decreased urea nitrogen and creatinine, and increased potassium, cholesterol, and triglycerides. Significant increases in serum calcium and phosphorous levels and alkaline phosphatase activity (bone isozyme) correlated with the histological changes in bone. In pGH-treated dogs, there was a dose-related normochromic, normocytic, nonregenerative anemia. The changes described above, except for the anemia, are related to either anabolic or catabolic effects of high doses of GH. Based on this study, it is concluded that the dog is a good model in which to evaluate the safety of GH secretagogues as well as compounds with GH-like activity.

Structure and function of bovine growth hormone. Bovine growth hormone as an experimental model for studies of protein-protein interactions

Growth hormone (GH) is a polipeptide that controls the differentiation, growth and metabolism of many cell types, and is secreted from the hypophysis of all vertebrate species tested so far. Despite the overlapping evolutionary, structural, immunological and biological properties, it is well-known that GHs from distinct mammalian species have significant species-specific characteristics. The main purpose of this review is to highlight bovine GH (bGH) structural features related to its species-specific properties. Novel interest in bGH is also aroused by the advent of biotechnological methods for production of recombinant proteins. In fact recombinant bGH will have a great importance in veterinary medicine research and as a 'high tech' drug that needs to be monitored in zootechnical productions.

The molecular evolution of vertebrate growth hormones: a pattern of near-stasis interrupted by sustained bursts of rapid change

It has been demonstrated previously that in mammals the evolution of pituitary growth hormone shows an unusual pattern, with an underlying slow rate and at least two sustained bursts of rapid evolution (in the artiodactyls and primates), during which the rate increased at least 25-fold. It is demonstrated here that a similar pattern applies for growth hormone evolution throughout the vertebrates, with a basal rate similar to that seen in mammals, but bursts of rapid evolution in the amphibia and the elasmobranchs, and several bursts in the teleosts. The placental growth-hormone-like proteins of primates show a similar pattern. It is argued that the bursts of evolution seen for growth hormone are a consequence of selection and that this may reflect changes in the functions of the hormone additional to its basic growth-promoting actions.

Determination of canine prolactin by use of a commercial heterologous enzymeimmunoassay kit

The present study evaluated a commercial heterologous enzymeimmunoassay (EIA) method for the determination of prolactin (PRL) in canine blood plasma and compared the results found with this heterologous method to the PRL concentrations measured by use of a commercial homologous PRL EIA. The heterologous PRL EIA was characterized by intra-assay coefficients of variation (CV %) of 3-5 % for replicate determinations, and inter-assay CV %'s of 5-7 % between means of duplicate determinations. The least detectable concentration was 0.1 microgram/L. A satisfying accuracy was settled by a recovery of added PRL not different from 100 % at varying PRL levels. The cross-reactivity (CR) to canine growth hormone (GH) was 5 %. Both methods outlined equally well the changes in PRL concentrations induced by administration of metoclopramid and bromocriptin; the specificity of both methods was further confirmed by a lack of response to clonidin GH stimulation test. The results achieved with the two methods were not identical despite of identical dose response relations. This difference in test results was, however, considered to be of minor practical importance if locally established reference ranges are used for evaluation of test results.

Cloning of the cDNAs coding for cat growth hormone and prolactin

Characterization of the prolactin (PRL) amino acid (aa) or cDNA sequences has not been reported for any member of the Felidae family. We cloned cat growth hormone (cGH) and cat PRL (cPRL) cDNA sequences from a feline pituitary cDNA library. High homology between species allowed bovine PRL(bPRL) and bGH cDNA clones to be used to identify clones encoding the 229-aa cPRL and 216-aa cGH sequences. The cGH protein is most homologous to pig and dog GH. Similarly, cPRL shares the most aa identity to pig PRL (pPRL). Northern blot analysis revealed the mRNA size for cGH and cPRL to be approx. 1 and 1.1 kb, respectively. These results reveal that GH and PRL from the Felidae family are highly conserved to other families of GH and PRL.

Cloning and characterisation of the rabbit growth hormone-encoding gene

The gene encoding growth hormone (GH) has been cloned from a rabbit genomic library, and its sequence has been determined. The rabbit GH gene is similar to other mammalian GH, being comprised of five exons and four introns. As in rodents and artiodactyls, the rabbit GH occurs as a single gene, with no evidence for a cluster of GH-like genes, as is found in primates. The amino acid sequence of rabbit GH is similar to that of pig GH and other conserved mammalian GH, and, like these, differs markedly from the available sequences of ruminant and primate GH. This provides further support for the idea that, in mammals, GH show a slow underlying rate of evolution which has increased markedly on at least two occasions.

An improved radioimmunoassay for the determination of canine growth hormone based on commercially available reagents

Determination of canine growth hormone (cGH) is of importance when evaluating the growth hormone status in dogs, for instance when diagnosing pituitary dwarfism and acromegaly. At present, analysis for the cGH content in canine blood has mainly been restricted to specialized laboratories which have had the capacity to develop suitable methods. We therefore formulated the objective of the present study to be the development of a generally accessible method utilizing commercially available reagents. We describe a radioimmunoassay (RIA) for the determination of cGH which was based on reagents developed for the determination of porcine growth hormone (pGH), thereby drawing benefit from the similarity between growth hormones from the two species. The RIA method was characterized by satisfying precision and accuracy parameters: intra- and inter-assay coefficients of variation (CV%) were 4-27% and 4-20%, respectively, depending on the cGH concentration of the samples. Recovery of added cGH and parallelism between standard curve and sample dilutions were acceptable, thus indicating identity between the calibrator system and the material under investigation (i.e. plasma samples). When measuring individual plasma samples or samples taken during clonidin response tests from normal dogs, dogs suffering from pituitary dwarfism and from dogs suffering from acromegaly, the results were comparable with previous findings.

Cloning and sequencing of cDNA encoding the cat growth hormone

A cDNA encoding cat growth hormone (Fc GH) has been isolated and sequenced. This is the first report of a feline GH nucleotide and deduced amino acid (aa) sequences. This cat pituitary cDNA resembles a typical mammalian pre-GH cDNA with its encoded mature hormone differing from dog GH only by a single aa residue.