Jocelyn Jumawan

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.

Effect of cortisone and thyroxine on acid glycosidases in rat forebrain and cerebellum during early postnatal development.

Abstract— l‐Thyroxine (200 μg/100 g B.W.) or cortisone‐acetate (5 mg/100 g B.W.), administered for 4 consecutive days, affected several lysosomal enzymes in forebrain and cerebellum of rats during various periods of the first month of postnatal development; their effect was age dependent as well as organ specific. Extending thyroxine or cortisone treatment to 7 days (from day 2 to 9) affected enzyme activity more than the 4‐day treatment period.

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 μg/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.

Inhibition of the cortisone-evoked increase of intestinal sucrase by actinomycin D.

Summary Administration of actinomycin D inhibits the cortisone-evoked increase of sucrase activity in the jejunum and ileum of suckling rats. An interpretation of the present study suggests that de novo protein synthesis was inhibited and prevented the cortisone-evoked increase of sucrase activity.

Isolation of Microvilli Fraction from Jejunal Mucosa and in vivo Incorporation of 14C-Leucine into Microvilli and Total Homogenate Protein of Suckling Rats

The rate of incorporation of 14C-leucine into protein of the jejunal mucosa and isolated brush border was compared after i.p. application in suckling rats. Whereas the peak in specific activity of the homogenate protein was attained 15 min after the pulse injection, specific activity of the brush border protein peaked after 60 min. The pattern of decay of specific activity of proteins indicated a strong reutilization of label. Determination of 14C radioactivity in urine of sucklings and in mother’s sera and milk have shown a circulation of 14C-labeled substances between the mother and offspring via the urine (offspring) and milk (mother) cycle.

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.

PRECOCIOUS INDUCTION OF RAT JEJUNAL SUCRASE BY TRIIDO THYRONINE |[lpar]|T3|[rpar]|: IN FETUSES BY ADMINISTRATION TO THE PREGNANT MOTHER AND IN SUCKLINGS BY ADMINISTRATION TO THE LACTATING MOTHER

Daily application of T3 (20 μg/100 g body wt) to female rats in the last (third) week of pregnancy elicits a precocious appearance of sucrase activity in fetal jejunum. Similarly, administration of T3 in much higher doses (1.25 mg/100 g body wt) from day 11 to 15 postnatally evokes a precocious appearance of jejunal sucrase activity in sucklings. T3 administration to lactating mothers is followed by decrease of TSH and T4 levels in sera of sucklings and by an increase in the T3 levels in the sera and milk of lactating mothers as well as in sera of sucklings.These experiments thus show: (a)sucrase activity is already inducible in fetuses, (b)T3 administration in very high doses to pregnant rats might be transferred to the fetus to the extent of still effective doses, (c)milk may function as an endocrine link between the mothers hormonal and metabolic systems and those of the sucklings.Supported by NIH Research Grant AM 14531)

449 JEJUNOILEAL GRADIENT OF SUCRASE ACTIVITY IS PROGRAMMED IN FETAL RATS IN UTERO

Sucrase activity is absent in the small intestine of fetal rats, but it increases during the weaning period. At the same time, its jejunoileal gradient, known to exist in most adult mammals, appears. Mechanisms leading to the expression of biochemical specialization of individual sections of the small intestine are not clear.Fragments of fetal rat jejunum and ileum (21-day old, CDF strain Charles River Farm) implanted under the kidney capsula of adult rats (Gastroent. 64:292 and J. End. 74:145) were assayed after 4 and 6 weeks for sucrase activity and compared with small intestine developing in situ.Results demonstrate that expression of jejunoileal gradient of sucrase activity is not dependent on direct contact of food; this factor as well as gastric, duodenal and pancreatic secretion might be responsible for its magnitude.(Support: NIH grant #AM HD 14531).

POSTNATAL CHANGES OF ACTIVITY OF ACID LIPASE AND NONSPECIFIC NEUTRAL ESTERASE IN RAT LIVER

Hydrolysis of the 4-methylumbelliferyl (4-MU) esters, oleate and nonanoate, was studied in homogenates of liver from suckling and adult rats. In both age groups, the pH optimum for 4-MU oleate hydrolysis was 4.0, whereas 4-MU nonanoate was hydrolyzed maximally at pH 6.5-7.0. Acid lipaee (4-MU oleate, pH 4.0) was resistant to inhibition by the organophosphate, dlethyl-p-nitrophenyl phosphate (E600), while nonspecific neutral esterase (4-MU nonanoate, pH 7.0) was sensitive to inhibition. Acid lipase and nonspecific neutral esterase differed substantially in the patterns of their postnatal development in the liver. Acid lipase activity was high during the suckling period and decreased after the third week of life to adult levels which were 50% of suckling levels. Nonspecific neutral esterase increased markedly with age, and adults attained levels 10 times those of sucklings. These experiments together with our concomitant findings of high acid lipase in the small intestine of suckling rats suggest the important metabolic role of acid lipase during the suckling period when fat intake is high. (Supported in part by NIH grants HD 08536 and HL 18723-01).