Growth patterns and hormonal profile of male rats with protein‐calorie malnutrition

Abstract

A condition of protein-calorie malnutrition was precipitated in young Sprague-Dawley male rats at 20 days of age using an 8% low protein diet (LPD). At five-day intervals for up to 50 days of age, the rats were studied to determine the effect of an LPD on the reproductive axis of the endocrine system. Daily monitoring of the body weight, as well as the consumption of food, kilocalories, and protein was conducted. The same parameters were followed over the identical time period in a group of animals desigated as controls which were fed a standard laboratory diet (SLD) containing 27% protein. The controls showed a linear growth rate over the 30-day experimental period. In comparison, the malnourished rats grew more slowly so that by 50 days of age, their mean body weight was 68.9 +/- 3.1 g as compared to 248.1 +/- 6.1 g for the controls. The daily food, kilocalorie, and protein intake by the experimental animals were also appreciably less. The pituitary gland, ventral prostate gland, testes and liver were smaller in the animals fed the LPD. This was observed as early as five days after initiating the dietary regimes and remained a consistent observation until the end of the experiment. In general, the absolute weights of these organs in the 50 day-old malnourished rats were similar to those found in 25 to 26-day-old animals fed the SLD. The relative weights of the pituitary gland and liver remained similar between the two animal groups. The testes and ventral prostate gland, however, were relatively smaller in the malnourished animals at nearly every time interval studied. On light microscopic examination of the testes, it was found that normal maturation of the germ cells failed to occur in all but one of the experimental animals, whereas maturation proceeded normally in the rats fed the SLD. Serum luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (PRL), and testosterone were lower in the malnourished animals at all ages studied. These hormones not exhibit the fluctuations that were seen in the controls and are typical in rats that are becoming sexually mature. The effect of protein deficiency on the concentration of the pituitary gonadotrophins was more varied. FSH concentrations were consistently lower, PRL was moderately affected, and LH remained essentially unchanged. Hypothalamic LH-releasing hormone was measured and found to be significantly less in the rats fed the LPD at most of the time intervals examined. These results indicate that the hypothalamo-hypophyseal-gonadal axis is impaired when the consumption of proteins and calorie is decreased. The possible involvement of extrahypothlamic centers in the control of hormone secretion in the protein-deficient rat is discussed.

Effect of Dietary Protein Levels on Sex Hormones in Growing Male Rats Kept under Constant Darkness

“…Herbert reported that serum testosterone, LH, and FsH concentrations in rats fed a low-protein diet (8% casein) were reduced compared with those of rats fed a highprotein diet (27% casein) [15]. In the present experiment, no difference in LH or FsH concentrations between the low-and normal-protein diets was found.…”

Quantitative morphological analysis of the pituitary gland in protein‐calorie malnourished rats

“…Food and caloric intake along with changes in body weights were monitored daily (Herbert, 1980a). Growth patterns of animals in each of the dietary groups were similar to those described in our previous work (Herbert, 1980a). Rats fed the LPD were both protein as well as calorie deficient as compared to their age-matched counterparts maintained on the 27% SLD.…”

“…Somatomedin production was measured in perfusates from livers of young rats fed a 4% protein diet and was 12.5% lower than that observed in age-matched controls ; serum levels of the hormone were similarly affected . Thus, the failure of rats to grow properly when maintained on a low protein diet Herbert, 1980a) is due in part to a complex series of events involving inadequate stimulation of hepatocytes by the pituitary gland for the synthesis of sufficient levels of somatomedin to induce chondrogenesis.…”

“…Investigators have used various paradigms to induce conditions of malnutrition such as chronic underfeeding or semistarvation (Pomerantz and Mulinos, 1939;Mulinos and Pomerantz 1940;Grewal et al, 1971;Howland 1975), starvation (Howland and Skinner, 1973;Pirke and Spyra 1981;Warnhoff et al, 1983), and consumption of either a protein-free diet (Horn 1955;Srebnik 1964;Srebnik and Nelson 1962) or one that contains lower than normal amounts of protein (Glass et al, 1979(Glass et al, , 1982Glass and Swerdloff, 1980;Herbert, 1980a;Weaker and Herbert, 1981;Herbert and Weaker, 1983). Each of these perturbations has led to a marked reduction in hypophyseal activity as well as in the function of the respective target organ(s).…”

Etude de la spermatogenèse chez le rat Wistar prépubère au cours d'une malnutrition protéino-énergétique suivie d'une réalimentation équilibrée

“…En abaissant le taux de protéines de la ration à 8 %, Herbert (1980) obtient chez le jeune Rat une inhibition du développement des tubes sémi-nifères, empêchant la mise en place complète de la spermatogenèse et par suite l'apparition de la puberté. C'est la totalité de l'axe hypothalamo-hypophysogonadique qui est déprimée dans ce cas comme le révèlent les dosages hormonaux (Campbell et al, 1977 ;Herbert, 1980 ;Glass et al, 19791 (Gosse et al, 1970), au cours de laquelle a lieu la puberté. L'évolution du poids testiculaire est biphasique (Desjardins et al, 1968 ;Brown-Grant et al, 1975) …”