Properties of angiotensin II receptors of domestic turkey (Meleagris gallopavo) adrenal steroidogenic cells

Invited review: Adrenocortical function in avian and non-avian reptiles: Insights from dispersed adrenocortical cells

Herein we review our work involving dispersed adrenocortical cells from several lizard species: the Eastern Fence Lizard (Sceloporus undulatus), Yarrow's Spiny Lizard (Sceloporus jarrovii), Striped Plateau Lizard (Sceloporus virgatus) and the Yucatán Banded Gecko (Coleonyx elegans). Early work demonstrated changes in steroidogenic function of adrenocortical cells derived from adult S. undulatus associated with seasonal interactions with sex. However, new information suggests that both sexes operate within the same steroidogenic budget over season. The observed sex effect was further explored in orchiectomized and ovariectomized lizards, some supported with exogenous testosterone. Overall, a suppressive effect of testosterone was evident, especially in cells from C. elegans. Life stage added to this complex picture of adrenal steroidogenic function. This was evident when sexually mature and immature Sceloporus lizards were subjected to a nutritional stressor, cricket restriction/deprivation. There were divergent patterns of corticosterone, aldosterone, and progesterone responses and associated sensitivities of each to corticotropin (ACTH). Finally, we provide strong evidence that there are multiple, labile subpopulations of adrenocortical cells. We conclude that the rapid (days) remodeling of adrenocortical steroidogenic function through fluctuating cell subpopulations drives the circulating corticosteroid profile of Sceloporus lizard species. Interestingly, progesterone and aldosterone may be more important with corticosterone serving as essential supportive background. In the wild, the flux in adrenocortical cell subpopulations may be adversely susceptible to climate-change related disruptions in food sources and to xenobiotic/endocrine-disrupting chemicals. We urge further studies using native lizard species as bioindicators of local pollutants and as models to examine the broader eco-exposome.

Influence of hot exposure on 12-week-old turkey hen physiology, welfare, and meat quality and 16-week-old turkey tom core body temperature when crated at transport density

The influence of hot conditions on 12-week-old turkey hens and 16-week-old toms while crated at transport density was evaluated. Forty-eight hens and 48 toms (8 birds per flock × 3 flocks × 2 humidity levels) were used in neutral treatments (trt; 20°C), and 16 hens and 16 toms (8 birds per flock × 1 flock × 2 humidity levels) were used in the hot trt (35°C). Birds were placed in crates at a transport stocking density of approximately 83 kg/m2, then inside a pre-conditioned chamber for 8 hours. Live shrink, core body temperature (CBT), heterophil/lymphocyte (H/L) ratio, and breast and thigh pH and color were recorded. Differences were declared significant at P ≤ 0.05. Live shrink after exposure to the 35°C trt (4.92%) was greater (P < 0.0001) than when birds were exposed to 20°C (1.48%). The 35°C trt (P < 0.0001) had higher Δ CBT (final minus initial) compared to the 20°C trt. The 35°C trt also caused higher (P < 0.0001) H/L ratio, 4.07 vs. 1.57 for the 20°C trt. Breast (P = 0.0110) and thigh pH levels (P < 0.0001) measured 27 h postmortem were lower for the 35°C trt at 5.64 and 5.73 compared to the 20°C trt at 5.70 and 5.92, respectively. Breast meat from birds exposed to 35°C was darker (P < 0.0001), while the color of thigh meat was unaffected. Toms quickly became distressed in the hot conditions, forcing those tests to be aborted. Only CBT data were analyzed. The CBT increased at a mean rate of 0.09°C/min for hens at both RH levels, while the CBT of toms increased at 0.12 and 0.18°C/min when exposed to 35°C, 30%; and 35°C, 80%, respectively. Exposure to hot temperatures caused higher CBT, greater live shrink, and greater H/L ratio. Toms were more greatly affected than hens to the hot trt, with CBT increasing at a greater rate.

Differential responses of the vasotocin 1a receptor (V1aR) and osmoreceptors to immobilization and osmotic stress in sensory circumventricular organs of the chicken (Gallus gallus) brain

Past studies have shown that the avian vasotocin 1a receptor (V1aR) is involved in immobilization stress. It is not known whether the receptor functions in osmotic stress, and if sensory circumventricular organs may be involved. An experiment was designed with four treatment groups including a 1h immobilization acute stress (AS) group, an unstressed acute control (AC), a third given an intraperitoneal (ip) hypertonic saline injection (HS) and isotonic saline controls (IC) administered ip. One set of chick brains was perfused for immunohistochemistry while a second was sampled for quantitative RT-PCR. Plasma corticosterone (CORT) and arginine vasotocin (AVT) concentrations were significantly increased in the immobilized and hypertonic saline groups (p<0.01) compared to controls. Intense staining of the V1aR occurred throughout the organum vasculosum of the lamina terminalis (OVLT) and subseptal organ (SSO)/subfornical organ (SFO). The immunostaining allowed the boundaries of the two circumventricular organs (CVOs) to be described for the first time in avian species. Both treatment groups showed marked morphological changes in glia within the OVLT and SSO/SFO. The avian V1aR, angiotensin II type 1 receptor (AT1R), and transient receptor potential vanilloid receptor 1 (TRPV1) mRNA levels were increased in the SSO/SFO in hypertonic saline treated birds compared to isotonic controls. In contrast, the latter two genes (AT1R and TRPV1) were significantly decreased in the OVLT of birds subjected to hyperosmotic stress, while all three genes were significantly up-regulated after immobilization. Taken together, results show a possible differential function for the same receptors in two anatomically adjacent CVOs.

Role of plasma ANG II in the excretion of acute sodium load in a bird with salt glands (Anas platyrhynchos)

This study was designed to further examine the role of plasma ANG II in the excretion of sodium in the Pekin duck, a bird with salt glands. Renal and extrarenal (salt gland) excretion of an intravenously administered isotonic saline load was monitored over a 4-h period in a group of eight birds under two conditions: the control condition, in which isotonic saline infusion decreased endogenous plasma ANG II from 102.6 to 16.5 pg/ml, and the experimental condition, in which ANG II suppression was prevented by intravenous infusion of a 3.5 ng. kg(-1). min(-1) dose of synthetic ANG II. ANG II infusion significantly decreased the total sodium excretion (by 15%), primarily via an inhibition of salt gland output. The results suggest that ANG II suppression facilitates the excretion of an administered sodium load in birds with salt glands.

Atypical angiotensin receptors may mediate water intake induced by central injections of angiotensin II and of serotonin in pigeons

Intracerebroventricular (i.c.v.) injection of serotonin (5-HT) in pigeons dose-dependently evokes a prompt and intense drinking behavior, which resembles that evoked by i.c.v. injections of angiotensin II (ANGII) in the same species. In the present study, we have examined the possible participation of central ANGII receptors in both ANGII- and 5-HT-evoked drinking behavior. The effects of i.c.v. injections of 5-HT (155 nmol), avian ANGII ([Asp(1),Val(5)]-ANGII, 0.1 nmol) or vehicle were studied in pigeons pretreated 20 min before with i.c.v. injections of the nonspecific ANGII receptor antagonist [Sar(1),Ile(8)]-ANGII (SAR; 1, 0.1 or 0.01 nmol), the AT(1) receptor antagonist losartan (2 or 4 nmol), the AT(2) receptor antagonist PD 123,319 (2 or 4 nmol) or vehicle (NaCl 0.15 M, 1 microl, n = 8/group). Immediately after treatment, they were given free access to water and drinking behavior was recorded during the next 60 min. At the doses presently used both 5-HT and ANGII treatments evoked comparable water intake amounts with similar behavioral profiles. While pretreatment with SAR dose-dependently reduced the water intake evoked by both 5-HT and ANGII, neither losartan nor PD 123,319 pretreatment affected the drinking induced by these treatments. The present results indicate that ANGII- and 5-HT-induced drinking in pigeons may be mediated by AT receptors possibly different from mammalian AT(1) and AT(2) receptors and suggest that activation of ANGII central circuits is a necessary step for the intense drinking induced by i.c.v. injections of 5-HT in this species.

Angiotensin receptor(s) in fowl

The cloning of the avian Ang II receptor shows that it is molecularly close to the AT(1)-type mammalian receptor. However, pharmacological characterization in transfected cells shows that, even though the avian receptor is coupled to the phospholipase C, as is the AT(1), its profile of specificity towards antagonists appears different from that of the two angiotensin II mammalian receptor types. The fowl Ang II receptor mRNA is expressed in classical adult target organs for Ang II and, interestingly, also in endothelial cells, but not in vascular smooth muscle cells. In the endothelial cells, it may mediate the peculiar vasorelaxation effect of Ang II already reported in the chicken. The recent description of the expression pattern in the chick embryo shows that the avian Ang II receptor is expressed in many different mesenchymal tissues, a feature which is the signature of the AT(2) mammalian receptor. Altogether, these data imply that the avian Ang II receptor is an atypical receptor that cannot be readily classified as either of the two mammalian Ang II receptor types and, therefore, reinforce the evidence for another Ang II receptor in the avian class.

Dietary protein restriction stress in the domestic chicken (Gallus gallus domesticus) induces remodeling of adrenal steroidogenic tissue that supports hyperfunction

The stress of dietary protein restriction in the immature domestic turkey (Meleagris gallopavo) induces adrenal steroidogenic hypofunction that is associated with an alteration in the proportion of density-dependent subpopulations of steroidogenic cells within the adrenal gland. In contrast, when imposed on immature chickens, this nutritional stressor induces long-term enhancement of adrenal steroidogenic function. However, whether this alteration in function is accompanied by a remodeling of chicken adrenal steroidogenic tissue as in the turkey is not known. To address this question, immature cockerels (2 weeks old) were fed established isocaloric synthetic diets containing either 20% (control) or 8% (restriction) soy protein for 4 weeks. Adrenal glands were processed for the isolation of defined, density-separable, adrenal steroidogenic cell subpopulations: three low-density adrenal steroidogenic cell subpopulations [LDAC-1 (rho = 1.0285-1.0430 g/ml), LDAC-2 (rho = 1. 0430-1.0485 g/ml), and LDAC-3 (rho = 1.0485-1.0500 g/ml)] and one high-density subpopulation [HDAC (rho = 1.0510-1.0840 g/ml)]. The steroidogenic function of these cell subpopulations was assessed. Protein restriction consistently, but differentially, enhanced maximal ACTH-induced corticosterone production by the subpopulations: values of LDAC-1, -2, and -3 and HDAC from protein restricted birds were, respectively, 116, 43, 33, and 20% greater than those of corresponding cell subpopulations from control birds. However, it had contrasting influences on maximal ACTH-induced aldosterone production by the cell subpopulations. Whereas the value of LDAC-1 from protein-restricted birds was 70% greater than that from control birds, the values for LDAC-2 and -3 were not different from those of the control, and the value for HDAC was 22% less than that of the control. Protein restriction also altered the cell subpopulation composition of the adrenal gland: compared to control, it increased the proportion of LDAC-1 by 46% and decreased the proportion of LDAC-3 and HDAC by 34 and 20%, respectively. Thus, dietary protein restriction increased the proportion of cells (i.e., LDAC-1) having the greatest enhancement in corticosteroid production. This pattern of remodeling of chicken adrenal steroidogenic tissue in response to dietary protein restriction contrasts sharply with the pattern that occurs in another galliform species, the domestic turkey.

Dietary protein restriction stress in the domestic turkey (Meleagris gallopavo) induces hypofunction and remodeling of adrenal steroidogenic tissue

In the present study, we investigated the influence of dietary protein restriction stress on adrenal steroidogenic function of the domestic turkey. Immature male turkeys (2 weeks old) were fed isocaloric synthetic diets containing either 28% (control) or 8% (restriction) soy protein for 4 weeks. Trunk plasma was processed for the determination of adrenocorticotropin (ACTH), corticosterone, aldosterone, and total 3, 5, 3'-triiodothyronine (T3). In addition, adrenal glands were processed for the isolation of defined, density-separable, adrenal steroidogenic cell subpopulations: three low-density adrenal steroidogenic cell subpopulations [LDAC-1 (rho = 1.0350-1.0490 g/ml). LDAC-2 (rho = 1.0490-1.0570 g/ml), and LDAC 3 (rho = 1.0370-1.0585 g/ml)] and a high-density subpopulation [HDAC (rho = 1.0590-1.0720 g/ml)], and the steroidogenic function of these cell subpopulations was evaluated. Protein restriction did not influence plasma ACTH However, it increased relative adrenal weight (mg/100 g body wt) (+37.8%) and plasma corticosterone (+317%). By contrast, it depressed plasma aldosterone (-51.2%). In addition, it caused a modest depression in plasma T3 (-25.9%). At the cellular level, protein restriction induced panhypofunction. Basal corticosteroid (aldosterone and corticosterone) production values of LDAC-1, -2, and -3 and HDAC from protein-restricted birds were, respectively, 42.9, 47.9, 30.8, and 57.5% less than those of corresponding cell subpopulations from control birds. In addition, maximal corticosteroid production values of LDAC-1, -2, and -3 and HDAC from protein-restricted birds, in response to ACTH, angiotensin II (AngII), and 25-hydroxycholesterol support, were depressed by 56.8, 55.1, 22.7, and 42.9%, respectively. Interestingly, LDAC-3 was relatively refractory to the influence of this stressor. By contrast, there was the lack of a concentration-dependent aldosterone response of LDAC-1 and -2 to AngII with protein restriction. This was not due to a failure in cell function since aldosterone responses of these cell subpopulations to ACTH and to 25-hydroxycholesterol support were apparent. In addition, the concentration of AngII receptors of cell subpopulations from protein-restricted turkeys, if anything, was greater than that of cell subpopulations from control turkeys. Protein restriction also altered the cell subpopulation composition of the adrenal gland: compared to control, it decreased the proportion of LDAC-2 by 42.3% and increased the proportion of LDAC-3 and HDAC by 68.7 and 302%, respectively. Thus, dietary protein restriction induces adrenal steroidogenic hypofunction in turkeys. In addition, the present study suggests that this nutritional stressor induces marked remodeling of the steroidogenic tissue in the turkey adrenal gland.

Angiotensin II receptor subtypes in the duck subfornical organ: an electrophysiological and receptor autoradiographic investigation

The pharmacology of angiotensin II (AngII) receptors was investigated in the brain of ducks using receptor autoradiographic and electrophysiological methods. Using 125I[Val5]AngII as a ligand, specific binding was observed in sections of the duck adrenal gland and in several brain areas involved in body fluid homeostasis. Displacement studies using the same antagonists as used for classifying mammalian AngII receptor subtypes revealed that the rank order of potencies in competition with AngII receptors in the adrenal gland and in the subfornical organ was: AngII > CGP-42112A > losartan > PD-123319. Electrophysiological recordings from spontaneously active neurons of duck SFO slices revealed that the majority of neurons could be excited by AngII (10(-7) M). The excitatory effect of AngII could be partially inhibited by CGP-42112A (10(-5) M), which proved to be more effective than equimolar losartan and far more effective than PD-123319. These data suggest that the neuronal AngII receptors in the SFO are pharmacologically distinct from the mammalian AT1- and AT2-receptors. Further, central AngII receptors of ducks share common pharmacological characteristics with AngII receptors in the duck adrenal gland and peripheral organs of other bird species.