Grubb B R, Bentley P J
Department of Anatomy, Physiological Sciences, and Radiology, North Carolina State University, College of Veterinary Medicine, Raleigh 27606.
J Comp Physiol B. 1992;162(8):690-5. doi: 10.1007/BF00301618.
Both avian corticosteroid hormones, aldosterone and corticosterone, increased short-circuit current across the wall of the ceca of the domestic fowl (Gallus domesticus) in vitro. About 80% of this short-circuit current was inhibited by the Na-channel blocking drug amiloride. Corticosterone was about ten times less potent than aldosterone in increasing short-circuit current and it exerted a similar maximal effect. Cortisol (an endogenous corticosteroid hormone in mammals but not birds) was about ten times less potent than corticosterone and this difference appeared to reflect the presence of the 17 alpha-OH group in cortisol. Carbenoxolene, which inhibits 11 beta-hydroxysteroid dehydrogenase, increased the effect of corticosterone. This effect is consistent with inhibition of the metabolism of corticosterone to 11-dehydrocorticosterone. The latter was found to be about 100 times less potent than corticosterone. The effects of both aldosterone and corticosterone (also dexamethasone) were abolished by the mineralocorticoid receptor antagonist spironolactone. The results suggest that corticosterone has an effect similar to aldosterone but in vivo its action may be depressed by the activity of 11 beta-hydroxysteroid dehydrogenase. The sensitivity of the cecal preparations to corticosterone indicates that this hormone could contribute to the regulation of transcecal Na transport (absorption) in vivo.
禽类皮质类固醇激素醛固酮和皮质酮，均可在体外增加家鸡（原鸡）盲肠壁的短路电流。该短路电流约80%可被钠通道阻断药物氨氯吡咪抑制。皮质酮增加短路电流的效力约为醛固酮的十分之一，但其最大效应相似。皮质醇（哺乳动物而非鸟类的一种内源性皮质类固醇激素）的效力约为皮质酮的十分之一，这种差异似乎反映了皮质醇中存在17α-羟基基团。抑制11β-羟基类固醇脱氢酶的羧苄青霉素增加了皮质酮的效应。这种效应与皮质酮代谢为11-脱氢皮质酮的抑制作用一致。后者的效力约为皮质酮的百分之一。醛固酮和皮质酮（还有地塞米松）的效应均被盐皮质激素受体拮抗剂螺内酯消除。结果表明，皮质酮具有与醛固酮相似的效应，但在体内其作用可能会被11β-羟基类固醇脱氢酶的活性所抑制。盲肠制剂对皮质酮的敏感性表明，这种激素可能有助于体内经盲肠的钠转运（吸收）调节。
