The binding of insulin (IMS) and glucagon (GL) on isolated rat hepatocytes during the process of liver regeneration after partial hepatectomy was determined. Adult male rats were subjected to 65-70 % partial hepatectomy, control animals were sham-operated. The binding of radioiodine labelled IMS and GL to isolated hepatocytes was determined 1, 2, 3 and 5 days after the surgery. The plasma levels of IMS and glucose and microviscosity of liver plasma membranes were also measured. The decrease of IMS receptor binding capacity was found 1, 2, and 3 days after operation. Mo differences in sham and partially hepatectomized groups in IMS binding were noted 5 days after operation. A single insulin injection during the process of regeneration did not affect these changes of IMS binding to hepatocytes. The increase of GL binding was observed on the third day after partial hepatectomy, however, on the 5th day no changes of GL binding to its receptors were noted. The plasma insulin and glucose levels were similar in both hepatectomized and sham-operated rats. The increase of plasma membrane microviscosity of hepatocytes during the process of liver regeneration and a negative correlation between IMS binding and membrane microviscosity were found. These results demonstrated significant changes in binding parameters of both IMS and GL receptors in hepatocytes during liver regeneration induced by partial hepatectomy.
Effects of early neonatal interventions on metabolic parameters later in life (s.c. late effects) were studied in rats using two models; namely, (a) the effects of premature weaning and (b) the effects of "dietary" manipulations during the suckling period (s.c. small vs. large litters), (a) Premature weaning of rats caused an earlier degeneration of spermiogenesis and elevated plasma cholesterol levels in adult animals when compared to levels found in animals weaned 12 days later (on day 30 after birth). In adult rats, radioiodine uptake in thyroid glands was lower in the group weaned prematurely. Premature weaning was followed by a decrease of corticosterone production in adrenal glands in adult animals; in female adult prematurely weaned rats, an elevated response of adrenal cortex to stressors was observed. Several other studies explored the "immediate" effects of early, premature weaning, (b) Early exposure to high fat diet evoked a hypercholesterolaemic response in adulthood following brief exposure to HF diet. Rats from litters reduced to 3 or 4 pups per mother on postnatal day 3 exhibited 2 days later plasma levels of cholesterol higher than in rats raised in large litters of 8 or 14. The difference between small and large litters was preserved for the whole lifespan of the animals. In adulthood, rats from small litters were fatter and had higher levels of plasma cholesterol and insulin. Other studies suggester that early dietary experience may regulate the pattern of drug metabolism in adult life. An inhibition of diurnal plasma corticosterone variation was found in rats overfed during the neonatal period and an increased stimulation of lipolysis by norepinephrine and lipogenesis by insulin was demonstrated in neonatally underfed rats. Interesting studies were reported in longitudinally studies in children: at the age of 9-12 year brest-fed children (for more than 6 months) had the highest cholesterol levels; on the other hand significantly increased levels of APO B, Apo Al, ATH index and Apo/B Apo A1 quotient (p<0.05) were found in the nonbreast-fed group (27 references).
Early studies suggested endocrine type mother-pup interaction: 13M administered to suckling rats appeared via the urine of the suckling and mother's milk in the circulation of litter mates who were not injected with iodine; levels of thyroxin in rat milk were influenced by the status of the thyroid gland of the lactating rat. Administration of TRH (thyrotropin releasing hormone) to lactating mothers led to an appearance of unaltered hormones in the milk and stomach content of sucklings. TSH (thyroid stimulating hormone) or ACTH (adrenocorticotropic hormone) when given orogastrically to suckling rats increased thyroid hormones and corticosterone serum levels in suckling rats. Functional effects of gastrointestinal administration of insulin, bombesin (mammalian analog of gastrin-releasing peptide) and epidermal growth factor (EGF) are reviewed in detail (32 references).