Renin, ACTH, and aldosterone during acute hypercapnia and hypoxia in conscious rats

Abstract

The control of aldosterone secretion may be altered during acute changes in arterial blood gases. We studied the blood gas, plasma electrolyte, renin (PRA), adrenocorticotropic hormone (ACTH), and aldosterone (ALDO) responses to acute hypercapnia (4 and 8% CO2), acute hypocapnic hypoxia (10% O2), acute severe normocapnic hypoxia (7% O2-4% CO2), and acute hypercapnic hypoxia (7% O2-8% CO2) in conscious, cannulated Long-Evans rats. Normoxia resulted in normal levels of PRA (6.9 +/- 2.0 ng.ml-1.h-1), ACTH (96 +/- 32 pg/ml), and ALDO (10 +/- 3 ng/dl). Hypercapnia had no effect on PRA but did lead to an increase in ACTH (to 298 +/- 69 pg/ml) and ALDO (to 33 +/- 7 ng/dl) during 8% CO2 exposure. Normocapnic hypoxia resulted in a significant increase in ACTH (to 196 +/- 14 pg/ml) and ALDO (to 30 +/- 3 ng/dl). Hypercapnic hypoxia resulted in the greatest increases in PRA (to 30 +/- 2 ng.ml-1.h-1), ACTH (to 397 +/- 114 pg/ml), and ALDO (to 41 +/- 5 ng/dl). We conclude that in conscious rats 1) hypercapnia (less than 80 Torr) had no significant effect on PRA, 2) isocapnic, severe hypoxia (Po2 approximately 34 Torr) increased ACTH, and 3) the combination of hypercapnia and hypoxia was a very potent stimulus to PRA, ACTH, and ALDO. The ALDO responses to increases in endogenous ACTH and angiotensin II appear to be normal in conscious rats during acute hypoxia and/or hypercapnia.

Adrenocortical responses to ACTH in neonatal rats: effect of hypoxia from birth on corticosterone, StAR, and PBR

“…As soon as a litter was completely delivered, the pups were weighed and cross-fostered (8-10 pups/dam), and the dam and its pups were moved to an environmental chamber and exposed to normobaric normoxia (21% O 2) or hypoxia (12% O2) as described in detail previously (28,36). We have previously shown that this exposure leads to arterial PO 2 levels in adults of about 50-55 Torr with sustained respiratory alkalosis with metabolic compensation (27,30,31).…”

Influence of juvenile housing conditions on the ventilatory, thermoregulatory, and endocrine responses to hypoxia of adult male rats

“…Hypoxia is a systemic stress that can activate the HPA axis (22,43). CORT levels increased following hypoxia, but, given their differences in HPA axis function, the lack of differences between NMS and control rats in this response was unexpected.…”

Direct modulation of basal and angiotensin II-stimulated aldosterone secretion by hydrogen ions

“…pH o ) has a modulatory role in the control of aldosterone secretion arose from correlations between plasma aldosterone concentration and acid-base status (Christleib et al 1975, Kassirer et al 1976, Perez et al 1977, 1979, Schambelan & Sebastian 1977, Scott et al 1978, Raff & Roarty 1988, Julian et al 1982. The premise developed further in light of the ability of alterations in pH o to affect aldosterone secretion in vitro (Muller 1965, Chiu & Freer 1979, Gilchrist et al 1983 Carroll et al 1986, Radke et al 1986a.…”

“…For example, aldosterone levels in plasma increased during diabetic ketoacidosis (Christlieb et al 1975, Scott et al 1978, Quigley et al 1982, metabolic acidosis (Perez et al 1977, 1979, Schambelan & Sebastian 1977 and acute respiratory acidosis (Raff & Roarty 1988). Conversely, during metabolic alkalosis (Kassirer et al 1967, Julian et al 1982, plasma aldosterone concentration decreased.…”