Effect of triiodothyronine injection on levels of triiodothyronine and thyroid-stimulating hormone in sera and milk of lactating rats and in sera of their sucklings; precocious development of jejunal alpha-disaccharidases in the sucklings.

Administration of high doses of triiodothyronine (T3) for 4 days to lactating rats evokes an increase in T3 levels in their sera and milk, as well as in the sera of pups suckled by them. Thyroid-stimulating hormone levels in sera of mothers and sucklings are decreased. Suckling rats of T3-treated mothers exhibit a precocious increase in the activity of jejunal sucrase and maltase as well as in activity of several liver acid beta-glycosidases.

Development of jejunoileal differences of activity of lactase, sucrase and acid beta-galactosidase in isografts of fetal rat intestine.

Jejunal and ileal segments from preterm rat fetuses were implanted under the kidney capsula of adult rats. Sucrase, lactase and acid beta-galactosidase activities were determined in the isografts at different times after implantation, and in corresponding segments developing in situ. Whereas fetal intestine contains considerable activity of acid beta-galactosidase and lactase, no sucrase activity is detectable. Similarly -- as in situ -- 4 weeks after the implantation the jejunal segment exhibited higher activity of sucrase and lactase than the ileal segment. Acid beta-galactosidase was more active in ileal than in jejunal segments -- both growing in situ as well as isografts. Experiments have thus demonstrated that the expression of the jejunoileal gradient of activity of the 3 enzymes studied does not depend on direct contact with food or gastric, pancreatic and biliary juices. This gives validity to the suggestion that the gradient may already be programmed in fetal intestinal tissue, but other factors active in situ might be responsible for its magnitude.

Prenatal development of acid beta-glycosidases in the rat liver, effect of triiodothyronine or cortisone administered to pregnant rats.

We have found that acid beta-galactosidase, beta-glucuronidase and N-acetyl-beta-glucosaminidase in the rat fetal liver increase during the last week of pregnancy. These enzyme activities were influenced by treatment of pregnant rats (daily from day 16) with L-tri-iodothyronine (20 or 50 microgram/100 gm b.w.) or cortisone acetate (10 or 50 mg/100 gm b.w.) as studied in their fetuses obtained on day 22 by caesarian section.

Effect of cortisone or triiodothyronine administration to pregnant rats on lysosomal hydrolases in fetal forebrain and cerebellum.

Triiodothyronine injected daily to pregnant rats for the last week of gestation (50 microgram/100 g b.wt) increased the specific activities of 5 acid glycosidases in the fetal forebrain and cerebellum. Cortisone (50 mg/100 g b.wt) administered in the same period had no effect on cerebellum acid hydrolases, but decreased their activity in the forebrain.

Comparison of the effect of various doses of thyroxine on jejunal disaccharidases in intact and adrenalectomized rats during the first 3 weeks of life.

Administration of D,L-thyroxine (T4) daily (25 or 250 nmol/100 g body weight/24 h) for 4 days increased jejunal activity in 15-day-old rats; no effect was seen in 8-day-old rats. Maltase activity was increased in 15-day-old rats only when a 250-nmol dose was used. Similar results were obtained in unoperated and adrenalectomized rats. Specific activity of lactase was not influenced in unoperated 8- and 15-day-old rats; it was decreased in adrenalectomized 8- and 15-day-old rats when treated with a 250-nmol dose of T4; in 15-day-old rats, it also responded to 25-nmol doses. The lowest dose used (2.5 nmol/100 g body weight) had no effect at all.

Characteristics and postnatal development of the acid lipase activity of the rat small intestine.

Acid lipase was identified in the rat small intestine by using esters of 4-methylumbelliferone as substrates. Maximum activity towards the oleate ester was found at pH 4.0. In adult animals, the activity of acid lipase exhibited both latency and sedimentability, indicating a lyosomal localization. The activity of acid lipase was practically the same along the height of the villus, thus paralleling the distribution of acid beta-galactosidase. In adult rats, the activity of acid lipase in proximal (jejunum) and middle (mid-jejunum) sections of the small intestine was practically the same and exceeded the activity in the distal (ileum) section by a factor of 2. In suckling rats, the activity of the enzyme in the mid-jejunum exceeded that in the jejunum and ileum by 2.5- and 1.5-fold respectively. During postnatal development, the acid lipase activity of the mid-jejunum showed a peak between days 10 and 15, at which time it exceeded the adult mid-jejunum activity by 5--6-fold.

Thyroxine-evoked decrease of jejunal lactase activity in adult rats.

Daily administration of L-thyroxine (20 micrograms or 200 micrograms/100 g body weight) to adult male rats decreased jejunal lactase activity by 35% after 2-, 3-, 4- and 10 days. Four days of injections of D-thyroxine (200 micrograms/100 g body weight/day) produced a similar decrease of lactase activity. Sucrase activity was uninfluenced except for a 30% increase after daily injections of L-thyroxine (200 micrograms/100 g body weight) for 10 days. Acid beta-galactosidase activity was unaffected by either D- or L-thyroxine.

Prenatal induction of sucrase activity in rat jejunum.

Daily application of cortisone acetate (10mg/100g body wt.) or L-tri-iodothyronine (20 microng/100g body wt.) to female rats in the last (third) week of pregnancy elicits a precocious appearance of jejunal sucrase in their foetuses.

Effect of cortisone or L-triiodothyronine administration to pregnant rats on the activity of fetal intestinal disaccharidases and lysosomal acid beta-galactosidase.

Activities of maltase, sucrase, lactase and acid-beta-galactosidase were studied in jejunum and ileum of term rat fetuses obtained by cesarian section. Female rats were either untreated or injected daily in the last (3rd) week of pregnancy with cortisone acetate (10 or 50 mg/100 g body weight) or L-triiodothyronine (20 or 50 microgram/100 g body weight). Two other control groups were injected with appropriate solvents. Cortisone or T3 treatment to mothers increased sucrase and maltase activity in jejunum and ileum of the offspring. Generally, higher doses of hormone were more effective. Lactase activity was increased by 25% in the jejunum by the higher dose of cortisone. Both doses of cortisone increased ileal lactase. Jejunal acid-beta-galactosidase activity was decreased in fetuses of T3-treated mothers.

Comparison of postnatal development of several acid glycosidases in the rat forebrain and cerebellum.

Changes of activity of several glycosidases (beta-galactosidase, beta-glucuronidase, N-acetyl-beta-D-glucosaminidase, alpha-D-mannosidase and alpha-L-fucosidase) were compared in the forebrain and cerebellum during postnatal development of the rat. Detailed analysis of the data showed similarities, but also substantial differences in their development in both organs. This is interpreted as an indication of the presence of common regulatory mechanisms, as well as of other factors which differently influence development of the glycosidases studied in both CNS parts.

Effect of thyroidectomy on the activity of alpha-glucosidases and acid hydrolases in the small intestine of rats during weaning.

Adrenalectomy performed on 14-day-old rats delayed the usual increase of sucrase and maltase activity as well as the decrease of acid beta-galactosidase, beta-glucuroindase and N-acetyl-beta-glucosaminidase activity during the third postnatal week. Since these changes were only delayed, the role of the thyroid was explored. Thyroidectomy performed simultaneously with adrenalectomy on 14-day-old rats did not influence the increase in body weight and growth of the small intestine (already slowed down by adrenalectomy), but caused a further substantial delay in the maturation of the enzyme profile of the small intestine. Our results indicate that the thyroid is involved in regulation of the hydrolases studied.