In vitro study of the intestinal brush border enzyme activities in developing anuran amphibian: Effects of thyroxine, cortisol, and insulin

Abstract

The effects of several hormones on intestinal brush border membrane enzymatic activities have been investigated in intestinal explants taken from the amphibian midwife toad at different developmental stages. Explants were treated for at least 2 days with thyroxine (0.1 microgram/ml of culture medium) or for 2 days with cortisol (25 micrograms/ml) or insulin (6 mU/ml). The hydrolases examined were maltase, trehalase, glucoamylase, and alkaline phosphatase. In the explants from tadpoles in prometamorphosis, thyroxine had no effect on hydrolase activities; cortisol increased the activity of only glucoamylase, and insulin increased activity of maltase, glucoamylase, and alkaline phosphatase. When the explants were taken from tadpoles at the beginning of climax, cortisol and insulin generally stimulated the enzyme activities studied. When taken from tadpoles at the end of climax, at the moment when the embryonic cells under the degenerating epithelium divide, cortisol and insulin had little effect on these activities. When the animals terminate their metamorphosis, the intestinal epithelium of the explants is totally newly formed (secondary epithelium). At this time, cortisol stimulated the activities of maltase, glucoamylase, and alkaline phosphatase, while insulin decreased the activities of maltase and glucoamylase.

Insufficiency of Thyroid Hormone in Frog Metamorphosis and the Role of Glucocorticoids

“…TH treatment of bullfrog tadpoles reared in thiourea decreased larval brush border hydrolytic enzyme activity, but adult levels of enzyme activity did not come about even after 15 days post treatment (71). TH treatment of small intestine cultured in vitro also caused larval cell degeneration (72), but adult epithelium failed to proliferate sufficiently (73), adult-type microvilli did not form (74), and adult-pattern lectin binding failed to occur (72). In addition, the adult epithelium achieved by natural metamorphosis and the epithelium achieved by TH treatment responded to GCs, specifically hydrocortisone, differently (75, 76).…”

Insufficiency of Thyroid Hormone in Frog Metamorphosis and the Role of Glucocorticoids

“…TH treatment of bullfrog tadpoles reared in thiourea decreased larval brush border hydrolytic enzyme activity, but adult levels of enzyme activity did not come about even after 15 days post treatment (71). TH treatment of small intestine cultured in vitro also caused larval cell degeneration (72), but adult epithelium failed to proliferate sufficiently (73), adult-type microvilli did not form (74), and adult-pattern lectin binding failed to occur (72). In addition, the adult epithelium achieved by natural metamorphosis and the epithelium achieved by TH treatment responded to GCs, specifically hydrocortisone, differently (75, 76).…”

Insufficiency of Thyroid Hormone in Frog Metamorphosis and the Role of Glucocorticoids

“…TH treatment of bullfrog tadpoles reared in thiourea decreased larval brush border hydrolytic enzyme activity, but adult levels of enzyme activity did not come about even after 15 days post treatment (71). TH treatment of small intestine cultured in vitro also caused larval cell degeneration (72), but adult epithelium failed to proliferate sufficiently (73), adult-type microvilli did not form (74), and adult-pattern lectin binding failed to occur (72). In addition, the adult epithelium achieved by natural metamorphosis and the epithelium achieved by TH treatment responded to GCs, specifically hydrocortisone, differently (75, 76).…”

Insufficiency of Thyroid Hormone in Frog Metamorphosis and the Role of Glucocorticoids

“…TH treatment of bullfrog tadpoles reared in thiourea decreased larval brush border hydrolytic enzyme activity, but adult levels of enzyme activity did not come about even after 15 days post treatment (71). TH treatment of small intestine cultured in vitro also caused larval cell degeneration (72), but adult epithelium failed to proliferate sufficiently (73), adult-type microvilli did not form (74), and adult-pattern lectin binding failed to occur (72). In addition, the adult epithelium achieved by natural metamorphosis and the epithelium achieved by TH treatment responded to GCs, specifically hydrocortisone, differently (75, 76).…”