1. Investigación

Postnatal development of the glucose and insulin balance in offspring of ethanol-treated and control rats has been studied. Newborn rats were separated from their mothers and placed with normal lactating, nonethanol-treated dams. Prenatal exposure to ethanol led to hypoglycemia on the first day of extrauterine life and a general tendency to hyperinsulinemia during the entire postnatal period studied. The glucose-tolerance test in weaned rats (30 days old) gave a greater and faster increase than controls in levels of both glucose and plasma insulin. At adult age (90 days) the response of blood glucose to an oral glucose load in offspring from ethanol-treated mothers was not different from that in offspring from controls, but the insulin response was higher. This abnormal insulin response, such a long time after the end of ethanol exposure, suggests either a permanent alteration in the pancreatic response, or a peripheral insulin resistance and/or differences in the rate of insulin degradation in these animals.

Female rats receiving ethanol in the drinking water before and during gestation (ET) were compared to pair-fed animals (PF) and normal controls (C) fed ad libitum. On the 21st day of gestation the maternal body and liver weight, blood glucose, and plasma protein concentrations were lower in ET and PF animals as compared to C. In contrast to C or PF mothers, ET-fed mothers had higher circulating P-hydroxybutyrate and triacylglyceride levels and P-hydroxy-butyrate/acetoacetate ratio. Liver triacylglycerides were increased whereas liver glycogen concentration was reduced in ET-fed animals. Only fetal body and liver weights and blood glucose were lower in both ET and PF than in C. Blood P-hydroxybutyrate was increased and liver glycogen was decreased only in ET fetuses. There were no differences among the groups in fetal circulating P-hydroxy-butyrate/ acetoacetate ratio, plasma proteins, and triacylglycerides or liver triacylglyceride content. Results indicate that certain changes in ET mothers are specifically produced by the ethanol intake rather than undemutritlon. Further, metabolic changes occurring in the fetus are influenced by the ethanol effects in the mother and these actions may be added to those directly produced by the ethanol crossing the placenta.

The in vitro metabolism of glycerol by epididymal fat pads from thyroidectomized rats daily injected with either 0, 0.1 or 1.8 μg of L-thyroxine/100 g body wt. was compared with that from intact controls. The basal as well as the adrenalin- or glucose-enhanced release of glycerol to the medium were similar in the tissues from all the groups. The effect of insulin in decreasing the lipolytic action of adrenalin was greater in the thyroidectomized animals treated with either O or 0.1 μg of thyroxine than in the other two groups. The utilization of p-1 4c]glycerol for the formation of CO2 and glyceride glycerol was increased in the thyroidectomized rats; this effect was smaller when the animals were treated with 0.1 μg of thyroxine and disappeared when they were treated with 1.8 μg. In the presence of glucose the difference in utilization of glycerol between the groups disappeared. The formation of fatty acids from glycerol was greater in the presence than in the absence of glucose and was similar in the hypothyroid animals and the controls. The effect of adrenalin in decreasing the utilization of [1-1 4C]glycerol was less in the tissues from hypothyroid rats than in the controls. The decrease of the action of adrenalin by insulin in the tissues from thyroidectomized rats treated with O or 0.1 μg of thyroxine was greater than in the controls. The increased capacity to form glyceride glycerol from glycerol in tissues from hypothyroid animals contributes to the high re-esterification of fatty acids described for these animals. The effect of glucose is explained in terms of its competition with glycerol for the synthesis of a-glycerophosphate.

1.8 or 25 µg of L-thyroxine/100 g body wt. were compared with intact controls (C). The appearance of radioacitvity in fatty acids 30 min after the i.p. injection•of (3-14C)pyruvate was reduced in adipose tissue and enhanced in liver of T+25, being no differences between the other groups and C. ( 14C)- Fatty acids are reduced with 3 h of fasting only in the adipose tissue of T+ 1.8 and C, while 24 h produces a reduction in liver in the T+ 1.8, T+25 and C, and in adipose tissue in the T+l.8 and C animals. The highest percentage of radioactivity was observed in the liver glyceride glycerol fraction, being greater in T+25 than in the other groups. Fasting produces an increment in the ( 14C)-glyceride glycerol fraction. being significant only in the hypothyroid animals in both liver and adipose tissue. The most sensitive parameter to fasting was the formation of ( 14C)-non-saponifiable lipid in both the C and T+ 1.8 animals, while it does not change in T+0 or T+0.I, but is enhanced within 24 h in the adipose tissue of T + 25. It is proposed that most of the observed changes are due to the other endocrine disfunction s which appear in hypo- and hyperthyroidism, as the in vivo results do not comply with in vitro effects of thyroxine on lipogenesis of others.

To determine adipose tissue cellularity in hypo- and hyperthyroidism, male rats were thyroidectomized after weaning (T) and injected daily with either 0, 0.1, 1. 8, or 25 µg of L-thyroxine/100 g body weight for 40 days. They were compared with intact controls (C). Both epididymal fat-pad weight and adipocyte diameter were reduced in T+0, T+0.1 and T+25 animals. When corrected per unit of body weight, the diameters of adipocytes from T+0 and T+0. l animals were larger than in the other groups. Those same animals have reduced absolute adipocyte number but not when corrected per unit of body weight. The fat-pad protein concentration varied conversely with the fat cell diameter. These findings indicate that thyroid hormone deficiency reduces thf proliferation of fat cells in parallel with body growth while hyperthyroidism causes reduction in the size, but not the number, of fat cells which corresponds to its depletion of fat storage.

A method is described for determining triacylglyceride concentration in small amounts of plasma. After ethanolic-KOH digestion of diluted plasma aliquots, samples were neutralized with MgSO4 and gly~erol was fluorimetrically assayed in supematants by the coupling of glycerokinase, pyruvate kinase, and lactate dehydrogenase catalyzed reactions. Values were corrected by free glycerol present in the non-digested samples. Digestions were performed at different times and temperatures in order to establish optimum conditions for recoveries and reproducibility. Parallel determinations before and after phospholipid removal showed that their presence in plasma did not interfere with the obtained values. This method is especially useful for running many samples in parallel and for determinations in small experimental animals in which the amount of plasma is very limited.

Triglyceride-rich rat lipoproteins (mainly VLDL), purified by ultracentrifugation and dialysis, were incubated for 120 min in the presence of epididymal fat-pad pieces from fed rats in media containing heparin. During this process, the lipoproteins were depleted of triglycerides and proportionally enriched with proteins, causing their increased density. After incubation, electron microscopic study of the triglyceride- rich lipoproteins revealed partially degraded structures, and some particles had atypical discoid flattened form and marked lamellar structure. These findings are in agreement with those of BLANCHETTE-MACKIE & Scow (l 976) in triglyceride hydrolysed chylomicrons and confirm their observation of monolayers formed by accumulated lipolytic products that move by lateral diffusion, giving rise to a spiral fold between the core triglycerides and the aqueous space.

To study the potential relationship between circulating triacylglycerol (TAG) levels and Iipoprotein lipase (LPL) activity in the newborn rat liver, pups from undernourished or normal control mothers were nursed by normal dams, and studied at 0, 1, 15 or 30 days of age. Plasma TAG levels and liver TAG concentration increased more in pups from undernourished mothers than they did in controls. At birth, liver LPL activity was similarly high in both groups but, whereas in controls it decreased progressively after birth, in pups from undernourished mothers it remained stable until 15 days of age. Results suggest that the hypertriglyceridemia present in pups from undernourished mothers may be responsible for the sustained high LPL activity in their liver which may enhance the hepatic uptake of circulating TAG.