Effects of methylprednisolone on electrolyte transport by in vitro rat ileum

Abstract

Administration of the glucocorticoid methylprednisolone (MP) (30 mg/kg body wt for 3 days) to rats increased intestinal mucosal guanylate cyclase and Na-K-ATPase activities, short-circuit current (Isc), electrical potential difference (PD), net Na absorption, and net Cl secretion and reversed HCO3 transport from secretion to absorption. In the MP-treated animals, removal of HCO3 from both the mucosal and serosal bathing solutions increased Cl secretion but did not alter the Isc, PD, and net Na flux. Removal of Cl abolished the MP-induced increase in Isc but did not affect the MP-induced changes in net Na and HCO3 fluxes. At 6 h, after a single dose of MP, stimulation of guanylate cyclase activity was already maximal, whereas Na-K-ATPase activity was not detectably altered. The changes in intestinal transport properties present 6 h after MP treatment and associated with the increased guanylate cyclase activity were an increase in Isc and PD and a reversal of net Cl absorption to net secretion. These results suggest that an initial response to MP administration is a persistent increase in intestinal guanylate cyclase activity that mediates an electrogenic Cl secretory process, then is followed by a superimposed effect of increased Na-K-ATPase activity that mediates an increase in net Na absorption.

Physiologic and Pharmacologic Effects of Glucocorticoids on Ion Transport across Rabbit Ileal Mucosa In Vitro

“…With respect to Na transport and IS.,) these findings agree withl previous in vivo observations on rat ileum (2). A comiparable in vitro study with rat ileum (20) differs with both in vivo rat data and our in vitro rabbit data; although MP treatment was found to increase net Na absorption, it was also found to stimulate net Cl secretion; MP treatment was also reported to increase mucosal cGMP concentration, suggesting that this change may be responsible for the observed Cl secretion (19 T4. This has been ascribed to a propylthiouracil effect on thyroid metabolism (28,29).…”

“…As shown in Table IIIB ECST has been previously shown to inhibit Na and Cl absorption in rabbit ileum, probably as a result ofan (19) and stimulates Cl secretion in vitro (20). Because cGMP has been postulated to mediate the action of ECST (11,17,18), it was suggested that the above two effects of MP treatment are causally related.…”

Na,K-ATPase in diabetic rat small intestine. Changes at protein and mRNA levels and role of glucagon.

“…High doses of other glucocorticoids have trophy and hyperplasia in rats with diabetes (23)(24)(25)(26). This hyalso been shown to increase Na,K-ATPase activity in rat small perplasia is also seen in renal tubules (21,47) but not in a intestine (9,57,58). As for K+, only extreme changes incomnumber of other organs tested.…”

Glucocorticoids and the Intestinal Environment

“…The effects of mineralocorticoids and glucocorticoids on intestinal water and ion movements are well known. Methylprednisolone for 3 days increased Na + K + adenosinetriphosphatase activity and Na + absorption [83]; it also increased guanylate cyclase activity and Cl -secretion in the jejunum and ileum 6 h after administration [84,85]. However, there is no direct information about the increase of water and ion secretion related with increased glucocorticoid secretions in different stressful conditions.…”