title: Role of mineralocorticoids and glucocorticoids in blood pressure regulation in normotensive rats.
abstract: The separate role of mineralocorticoid and glucocorticoid hormone action in maintaining arterial pressure was studied in normotensive rats. Four groups were prepared: adrenalectomized (ADX) rats given 6 micrograms aldosterone/24 h (ALDO; n = 9) or 10 micrograms dexamethasone/24 h (DEX; n = 9) by intraperitoneal Alzet pumps, shamoperated controls (control; n = 10) and ADX rats with no hormone replacement (ADX; n = 9). All groups were given 1% NaCl + 2.5% glucose drinking solution. Measurements of plasma corticosterone and aldosterone and urinary aldosterone excretion confirmed the adequacy of the experimental groups. Forty-eight hours after ADX or sham, base-line intra-arterial mean arterial pressure (MAP) in conscious undisturbed rats was similar in the four groups. Captopril (1 mg/kg iv) produced a similar reduction in MAP in ALDO (-11 +/- 2 mmHg) and DEX (-12 +/- 1 mmHg) groups, despite a lower plasma renin activity (PRA) in ALDO (2.0 +/- 0.7 and 6.0 +/- 1.5 ng X ml-1 X h-1, respectively; P less than 0.05). dP (Me)TyrAVP (50 micrograms/kg iv) caused a greater decrease in MAP in ALDO (-15 +/- 3 mmHg) than in DEX (-8 +/- 1 mmHg; P less than 0.05). Combined blockade with both antagonists resulted in a greater MAP reduction in ALDO (-29 +/- 4 mmHg) than in DEX (-15 +/- 4 mmHg; P less than 0.05). These results indicate that glucocorticoid hormone action maintains arterial pressure in ADX rats by mechanisms similar to normal rats and largely independent of the renin-angiotensin system and vasopressin. In contrast, mineralocorticoid replacement alone in ADX rats requires increased participation of both peptide systems for maintenance of arterial pressure.
mesh_terms: D000315:Adrenalectomy; D000450:Aldosterone / Q000378:metabolism / Q000494:pharmacology*; D000803:Angiotensin I / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002216:Captopril / Q000494:pharmacology; D003345:Corticosterone / Q000097:blood; D003907:Dexamethasone / Q000494:pharmacology*; D004573:Electrolytes / Q000097:blood; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012083:Renin / Q000097:blood
chemical_list: D004573:Electrolytes; D000450:Aldosterone; D003907:Dexamethasone; D000803:Angiotensin I; D002216:Captopril; D012083:Renin; D003345:Corticosterone