Interactions between cyclosporin A, indomethacin and 16,16-dimethyl prostaglandin E2: effects on renal, hepatic and gastrointestinal toxicity in the rat

Rats were treated for 3 or 14 days with cyclosporin A (CsA, 50 mg/kg) or indomethacin (2 or 5 mg/kg) either alone or in combination, or with CsA plus 16,16-dimethylprostaglandin E2 (DMPGE2, 0.25 mg/kg). Hepatic and renal function were unaffected by treatment with indomethacin at either dose and only at the higher dose was severe intestinal ulceration observed. CsA caused renal and hepatic toxicity, evidenced by increased urine N-acetyl-beta-D-glucosaminidase activity, serum urea, creatinine and bilirubin and decreased serum albumin and total protein. In rats cotreated with CsA and either dose of indomethacin the increases in serum urea and creatinine and decreases in serum albumin and total protein were accentuated, but serum bilirubin was not further increased. Intestinal lesions were present in rats treated for 14 days with CsA plus the lower dose of indomethacin, but not in rats treated with either drug alone. In rats treated with DMPGE2 plus CsA, serum urea and creatinine were normal and urine N-acetyl-beta-D-glucosaminidase activity was reduced compared to rats treated with CsA alone, but DMPGE2 cotreatment had no effect on the CsA induced hyperbilirubinaemia. Hepatic microsomal cytochrome P-450 concentration and aminopyrine N-demethylase activity were lower in rats treated with CsA plus indomethacin than in untreated rats or those treated with either drug alone. Coadministration of indomethacin or DMPGE2 had no effect on serum trough CsA levels. The results are interpreted as showing an exacerbation by CsA of the intestinal toxicity of indomethacin, an increase by indomethacin in the renal toxicity of CsA and a protection by DMPGE2 against CsA renal toxicity. Possible mechanisms involving drug interactions and either hepatic cytochrome P-450, renal cyclooxygenase or other renal sites are discussed.

Cyclosporin A-induced nephrotoxicity in the rat: relationship to increased plasma renin activity

Cyclosporin A (CsA; 50, 100 or 150 mg/kg) was administered by gavage, daily for 4 days, to groups of normotensive rats. An additional group of animals received the drug vehicle. CsA-induced nephrotoxicity, characterized by reduced glomerular filtration rate (GFR) and urinary sodium flow, enzymuria and proximal tubular cell damage was accompanied by elevated plasma renin activity (PRA). These changes were dose-related at 50 and 100 mg/kg CsA, but were not increased by administration of 150 mg/kg. Circulating trough drug levels were related to dosage. Four days after CsA withdrawal in animals given 50 mg/kg, there was reduced nephrotoxicity and PRA had returned to normal, even though circulating CsA levels had not diminished. Rats given 100 and 150 mg/kg, however, showed no reduction in nephrotoxicity or in PRA. Hyperglycaemia was evident at 4 days in animals given 100 and 150 mg/kg CsA and persisted 4 days after drug withdrawal. There were no accompanying abnormalities in islet cell structure. Continuous administration of CsA (50 mg/kg) to rats for 14 days caused elevated PRA on day 4 but a return to normal levels by day 7. In contrast, significant GFR impairment was evident by day 7 whilst enzymuria was significantly increased from day 4 onwards. CsA nephrotoxicity in the rat is clearly associated with activation of the renin-angiotensin-aldosterone system. Possible mechanisms leading to increased renin release are discussed.

Tumours acquire their vasculature by vessel incorporation, not vessel ingrowth

This study was designed to investigate the early development of tumour circulation using a transplantable mouse mammary adenocarcinoma. Tumour cells (10(6] were injected subcutaneously into the flank and groups of treated mice were killed at 24 h intervals up to 12 days; the tumours and surrounding tissues being processed by standard histological methods. Sections of tumour were sub-divided into neoplastic tissue, vessels and connective tissue using computer-assisted morphometric techniques: the host tissue around the tumour was similarly quantified for vessels and connective tissue. With increasing tumour size, the proportion of vessels within tumours rapidly increased to reach a plateau of approximately 1.5 per cent of tumour volume, a 400 per cent increase on the vascular density of normal subcutaneous tissue. Within tumours, vascular density was always higher at the periphery than the centre. The most pronounced increase in vascular density affected the host tissue around the tumour. It is not clear why vascular development is most prominent outwith the tumour when postulated angiogenic factors, such as tumour angiogenesis factor, are presumably released within. Our results imply, however, that tumours acquire their vasculature by infiltration into, and expansion between, a network of newly formed vessels in the surrounding connective tissue.

The influence of enalapril or spironolactone on experimental cyclosporin nephrotoxicity

Adult Sprague-Dawley rats treated daily for 14 days with 50 mg/kg cyclosporin A (CsA) exhibited nephrotoxicity, characterized by reduced glomerular filtration rate, decreased urinary sodium and potassium flow, tubular enzymuria and proximal tubular structural damage. Elevations in plasma renin activity (PRA) were observed on day 4, but returned to normal within 7 days. Co-treatment of animals for the 14 day period with enalapril (8 mg/kg/day), a potent inhibitor of angiotensin converting enzyme (ACE), or spironolactone (25 mg/kg/day), the distal tubular antagonist of aldosterone, reduced the nephrotoxicity, although PRA remained elevated. Neither enalapril nor spironolactone affected circulating CsA levels. These data suggest that the action of aldosterone on the distal tubule may be important in the pathogenesis of CsA nephrotoxicity.

Congenital leukaemia: an unusual cause of stillbirth

Three cases of congenital leukaemia associated with hydrops and intrauterine death are described. The leukaemic infiltrates, which involved both the infants and the placentas, were of monocytic, lymphoblastic, and myeloblastic types, respectively. The general lack of recognition of the condition is probably due to inadequate histological examination of the stillborn infant and the placenta.

A comparative toxicological study of cyclosporine and Nva2-cyclosporine in Sprague-Dawley rats

Adult, male Sprague-Dawley rats were given 50 mg/kg cyclosporine (CsA), cyclosporine G (nor-valine2-cyclosporine [CsG], or drug vehicle by orogastric intubation every 24 hr for 14 days. Both drugs profoundly suppressed humoral immune responses. Similar trough whole-blood cyclosporine levels were recorded in each group at days 7 and 14. In CsA-treated animals, significant lymphopenia was evident on day 14, together with monocytosis and neutrophilia. Only the monocytosis was seen in the CsG group. CsA and CsG both caused significant impairment of renal function by day 7, although at this time the effect was less marked with CsG. In both drug-treated groups, there was evidence of further deterioration in glomerular filtration rate (GFR) by day 14. A significant rise in enzymuria was also recorded in each group. Typical cyclosporine-induced proximal straight tubular cell vacuolation was evident in four of the eight rats given CsG and in three of seven CsA-treated animals. Liver function was also significantly impaired in both CsA and CsG groups. These data show that, at the selected dose, CsG shares the nephrotoxic and hepatotoxic properties of CsA. The extent to which these effects of CsG are dose-related and the true clinical potential of this cyclosporine analogue have yet to be evaluated.

Inhibition of drug-induced eosinophilia by cyclosporin A

Administration of cyclophosphamide to Sprague-Dawley rats 2 days before immunization with ovalbumin in complete Freund's adjuvant resulted in a striking blood, bone marrow, and tissue eosinophilia. The number of circulating eosinophils reached a maximum (50-fold increase above normal) 2 weeks after immunization, and eosinophils were also prominent in bone marrow, lymph nodes (paracortical areas), spleen (white and red pulp), and liver. The eosinophilia could be inhibited by daily oral administration of cyclosporin A (CsA), although its effect was dependent both on the duration of treatment and on the dosage of CsA. A similar, inhibitory action of CsA was demonstrated with respect to methotrexate-induced eosinophilia. This experimental model may prove useful in the study of factors regulating eosinophil production and in examining the prospective value of CsA in the treatment of conditions where eosinophils play a central role.

The predictive value of enzymuria in cyclosporin A-induced renal toxicity in the rat

The acute nephrotoxic properties of cyclosporin A (CsA) were investigated in normotensive, adult male Sprague-Dawley rats. Animals received either 50 or 100 mg CsA/kg by gastric intubation for 7 days. Within 24 h, significant increases in urinary N-acetyl-beta-D-glucosaminidase (NAG) and gamma-glutamyl transpeptidase (gamma GT) activity were observed at both doses of CsA. Renal function abnormalities, however, were not apparent until 2 days (100 mg/kg) or 7 days (50 mg/kg). Progressive increases in enzymuria were evident in both groups between 1 and 4 days, at which later time proximal straight tubular cell damage was first observed. The data obtained using this model clearly demonstrate that enzymuria provides a sensitive index of acute CsA-induced renal cell damage and that enzymuria precedes detectable renal functional and structural abnormalities.

Schistosoma mansoni surface glycoproteins. Analysis of their expression and antigenicity

Surface glycoproteins from newly transformed schistosomula of Schistosoma mansoni have been identified by surface radioiodination and lectin-affinity chromatography. From the glycoconjugates bound by the three lectins used, concanavalin A, peanut agglutinin and fucose-binding protein, only in the concanavalin-A-bound fractions were glycoproteins identified. Changes in concanavalin-A-binding glycoproteins were detected after transformation and early maturation of the schistosomula. Some glycoproteins disappeared (Mr 38 000, 29 000 and 25 000), some appeared independently of host molecules (Mr 19 000), others only appeared after culture in human serum (Mr 45 000). Two major glycoproteins of Mr 32 000 and 16 000 were detected on all stages examined. Within the total set of surface glycoproteins identified on 3-h schistosomula only the strong Mr-38 000-32 000 complex was found to be antigenic. Thus many major low-molecular-mass surface glycoproteins of the parasite are not recognised as antigens by immune animals. The separation of only the Mr-38 000-32 000 antigens by concanavalin A affinity chromatography indicates the feasibility of using this method in conjunction with immunoaffinity columns to purity these molecules.

Renal function in rats treated with cyclosporin following unilateral nephrectomy

The effects of oral cyclosporin A (25 mg/kg/day) on renal function and structure in groups of normal, laparotomized and unilaterally nephrectomized DA rats was assessed over a 4-week period. In each group, the drug caused impairment of function, although there was evidence of improvement during the course of the study. Cyclosporin A toxicity was most marked in the nephrectomized animals, where histological examination at 4 weeks revealed extensive damage to proximal straight tubular cells. Only minimal structural damage was observed in the two other groups. Cyclosporin A concentrations in whole blood and kidney were estimated by radioimmunoassay at 4 weeks. Similar drug levels were found in normal, laparotomized and nephrectomized animals, except for an unexplained fall in blood levels in the laparotomy group. The significance of these observations is discussed in the context of current knowledge concerning the physiological effects, toxicology and pharmacology of cyclosporin A.

Immunosuppressive activity and toxicity of cyclosporin A in rats pretreated with high dose cyclophosphamide

Cyclophosphamide (Cy; 150 mg/kg) was administered (i.p.) to groups of Sprague-Dawley rats, followed two days later by immunization with ovalbumin (OVA). From that time, cyclosporin A (CsA; 25 mg/kg) or its vehicle was given (p.o.) for a further 13 days. Control animals tested 14 days after immunization, showed strong Arthus-like and modest delayed-type skin reactions to OVA, in contrast to almost total inhibition in animals tested with Cy, CsA or both. Similar effects were observed with respect to serum anti-OVA antibody levels. Despite itself producing lymphopenia, CsA had no additional effect on the lymphocyte depletion caused by Cy. Both drugs, either alone or in combination, caused neutrophilia and monocytosis. An additional eosinophilia due to Cy was prevented by CsA. Cy induced splenomegaly, nodal extramedullary haemopoiesis and increases in both tissue eosinophils and marrow neutrophils. There was also lymphoid depletion in both spleen and lymph nodes which was enhanced by CsA. Thymic lymphoid atrophy was found only when CsA was given. Despite the powerful immunosuppressive properties of both drugs, detailed biochemical and structural analyses showed no other synergistic toxicity, apart from modest hepatic abnormalities. In particular, there was no enhancement of the nephrotoxicity of CsA.

Prevalence of polyps in an autopsy series from areas with varying incidence of large-bowel cancer

The results of this multicentre autopsy study emphasize the relationship between the prevalence of adenomas and the incidence of large-bowel cancer. The highest proportion of autopsies with adenomas was observed in the area with the highest incidence of large-bowel cancer. The segmental distribution of adenomas within the colon was found to be similar to the site distribution of cancer. However, the lowest proportion of adenomas was found in the rectum, the segment in which cancer is most frequent. The latter finding suggests that either the adenoma-carcinoma sequence is a less important pathway in the pathogenesis of rectal cancer, or that more rectal than colonic adenomas become malignant. The high proportion of hyperplastic polyps in the rectum, and statistically significant regional differences following the same patterns as the incidence of rectal cancer suggest that there could be at least an indirect relationship between hyperplastic polyps and cancer of the rectum. Adenomas of both colon and rectum were more frequent in men than in women, contrary to findings with colon cancer. However, as for colon cancer, the sex ratio of adenomas changed with age, from slightly below unity in persons under 65, to above unity for those aged 65 and over. A major difficulty that emerged was the histological identification of "polyps" because of the degree of autolysis of epithelial cells in the mucous membrane, and this difficulty largely contributed to the poor consistency of histological reporting. Regular consistency surveys of histological preparations should be recommended in any type of multicentre study in which histological examination is included.

Prolonged survival of rat renal allografts after multiple allogeneic pregnancies: strain specificity and role of erythrocyte antibody rosette inhibiting antibodies

The influence of allogeneic pregnancies on the survival of subsequent rat renal allografts was investigated in three rat strain combinations. Multiple but not single pregnancies produced significantly more long-term surviving kidney grafts than were found in virgin animals; the effect was specific for paternal antigens, as multiple pregnancies by an unrelated strain did not prolong kidney graft survival. In the multiparous groups, those animals with long-surviving grafts had significantly higher levels of non-cytotoxic antibodies against paternal strain B-lymphocytes (detected by the erythrocyte antibody rosette inhibition assay) than did animals which rejected their grafts. The results show that multiple pregnancies may produce a state of specific unresponsiveness to paternal antigens, similar to enhancement, which is marked by the presence of non-cytotoxic antibodies against paternal B-lymphocytes. It is suggested, therefore, that enhancement may be one of the protective mechanisms which prevent rejection of the fetus during pregnancy.

Amelioration of cyclosporin-induced nephrotoxicity in rats by induction of hepatic drug metabolism

The aim of this study was to determine the effect of altered hepatic drug metabolism on the nephrotoxic and immunosuppressive properties of cyclosporin A (CsA) in the rat. From a consideration of the structures of those CsA metabolites identified so far, it seemed probable that the metabolism of CsA would occur at the hepatic cytochrome P-450 (cyt P-450) enzyme system. CsA (50 mg/kg/24 hr) administered orally for 14 days resulted in significant increases in both serum urea concentration and urinary N-acetyl-beta-D-glucosaminidase activity, accompanied by renal proximal tubular vacuolation. The concomitant administration of either Aroclor 1254 (25 mg/kg/24 hr, i.p.) or phenobarbitone (PB) (40 mg/kg/24 hr, i.p.) but not 3-methylcholanthrene (3-MC) (15 mg/kg/72 hr, i.p.) resulted in abolition of the nephrotoxicity, assessed both biochemically and histologically, whilst the suppressive effect on the humoral response to SRBC was unaltered. Phenobarbitone also significantly decreased serum CsA concentrations. These results suggest that the PB-inducible set of cyt P-450 isoenzymes may be responsible or partly responsible for hepatic CsA metabolism.

Cyclosporine-induced fetotoxicity in the rat

Female Lewis rats mated with DA male rats were given 25 or 10 mg/kg/day cyclosporine (CsA) from the time of mating to 20 days postcoitus when autopsies were performed. At the higher dose, characteristic drug-induced pathological changes in the mother were accompanied by a striking fetotoxic effect, resulting in a high incidence of fetal mortality or in runting. In addition, fetal kidneys that could be examined showed evidence of CsA-induced proximal tubular cell damage. These abnormalities were not found at the lower dosage of CsA. The fetotoxicity observed at 25 mg/kg did not appear to be dependent on major histocompatibility differences between parental strains, since it was also observed, at the same dosage, in syngeneically mated female Lewis rats.

Effects of cyclosporin A on fetal development in the rat

The fetotoxicity of cyclosporin A (CsA) was examined in multiparous Sprague-Dawley rats given the drug (25 mg/kg/day) during different phases of gestation, the effects on the outcome of pregnancy being ascertained on day 19. CsA given from days 1 to 7 caused a small but significant reduction in litter size, with no significant increase in the number of resorptions. When the drug was administered from day 8 to 14 there was no significant change in litter size, but a very striking increase in the incidence of resorptions. This fetotoxic effect was also evident but less marked when the drug was withheld until day 15. Reduction in fetal weight was only present in the group given CsA from days 8 to 14. In surviving fetuses the presence of focal decidual necrosis was more frequent in mothers receiving CsA, suggesting a possible mechanism whereby CsA may mediate its fetotoxic effects.

Inhibition by cyclosporin A of IgE production and cyclophosphamide-induced eosinophilia in rats immunized with non-parasite antigens

Administration of cyclosporin A (CS-A; 25 mg/kg daily) to rats from the time of immunization with ovalbumin (OVA) in complete Freund's adjuvant abolished the production of anti-OVA antibodies, including IgE. Cyclophosphamide (Cy; 150 mg/kg) given 2 days before immunization also inhibited specific antibody production but at the same time induced a striking eosinophilia. Combined administration of both drugs resulted in the inhibition by CS-A of the Cy-induced eosinophilia. The results suggest that IgE synthesis and eosinophil proliferation may be under the control of separate T cell subsets. This rat model may prove useful in studies on the regulation of eosinophil production and the role of these cells in disease processes.

IgA nephropathy is not a rare disease in the United Kingdom

A retrospective analysis of all renal biopsies performed in the Grampian Region of Scotland during 1977-1980 revealed that IgA nephropathy was the most frequently encountered glomerular lesion. The commonest indications for renal biopsy were the presence of asymptomatic urinary abnormalities (90/184; 48.9%) especially asymptomatic haematuria (42/184; 22.8%). A histological diagnosis was made in 36 of the 42 patients presenting with asymptomatic haematuria (85.7%); 16 of the 26 cases of IgA nephropathy presented in this way. Overall, IgA nephropathy was detected in 14.1% of all biopsies and accounted for 21.8% of primary glomerular diseases. This study indicates that IgA nephropathy is apparently more common in Grampian than elsewhere in the United Kingdom. However, it is suggested that this does not represent a true variation in the prevalence of the condition; IgA nephropathy is probably a common cause of haematuria in the United Kingdom.

Inhibition of contact sensitivity reactions to DNFB by topical cyclosporin application in the guinea-pig

Contact sensitivity skin reactions to dinitrofluorobenzene (DNFB) were inhibited by twice daily topical application of cyclosporin (CsA, 2%) in normal guinea-pigs and in those with enhanced contact sensitivity reactions following pre-treatment with cyclophosphamide. In contrast to oral administration of CsA (25 mg/kg) for 4 days, topical application of the drug over the same period did not result in systemic absorption (as measured by radioimmunoassay) or in any evidence of nephrotoxicity.