Adrenocortical hormones and absorption of macromolecules by the small intestine of the young rat

Maternal obesity eliminates the neonatal lamb plasma leptin peak

A neonatal peak in rodent plasma leptin plays a central role in regulating development of the hypothalamic appetite control centres. Maternal obesity lengthens and amplifies the peak in altricial rodent species. The precise timing and characteristics of the neonatal leptin peak have not been established in offspring of either normal or obese mothers in any precocial species. We induced obesity by feeding female sheep for 60 days before conception, and throughout pregnancy and parturition with 150% of the diet consumed by control ewes fed to National Research Council recommendations.We have reported that mature offspring of obese sheep fed similarly exhibited increased appetite, weight gain and obesity in response to ad libitum feeding at 19 months of age. We observed a leptin peak in lambs of control ewes between days 6 and 9 of postnatal life, earlier than reported in rodents. This peak was not present in lambs born to obese ewes. The leptin peak in lambs born to control ewes was not clearly related to any changes in plasma cortisol, insulin, triiodothyronine, IGF-1 or glucose. However, there was a significant increase in cortisol at birth in lambs born to obese ewes related to an increase in leptin in the first day of life. We conclude that the increased cortisol seen in lambs of obese sheep plays a role in disrupting the normal peak of leptin in lambs born to obese ewes thereby predisposing them to increased appetite and weight gain in later life.

The neonatal cerebellum: the highest level of glucocorticoid receptors in the brain

We investigated the postnatal development of glucocorticoid receptors (GR) in rat cerebral cortex, hippocampus, olfactory bulbs and cerebellum during a period when cell proliferation, including neurogenesis in the latter 3 brain parts, is intensive. The concentration of GR was determined as the specific binding of [3H]dexamethasone to the cytosol stabilized against the inactivation of unoccupied receptor molecules by sodium molybdate. Unoccupied GR levels were found to increase during the first week, most rapidly in the cerebellum, where it reached the maximum during the second week. Specific binding of [3H]dexamethasone to the cerebellar nuclear fraction has already been present at days 8 and 15. By the end of the second week the cytosolic unoccupied GR begin to decline in the cerebellum. Total receptor binding, however, estimated in adrenalectomized animals does not decline. On the other hand, at day 8 adrenalectomy did not reveal more receptors than obtained in intact animals. Large numbers of GR in the neonatal cerebellum may specifically mediate the adverse effects of glucocorticoids on the cerebellar development during the period when the intensive morphogenetic processes take place in this part of the brain.

Adrenal function and passive immunity in the dystocial calf

Dystocial calves were tested for their ability to absorb colostral immunoglobulins and establish a competent passive immunity. Twenty dystocial and 20 eutocial calves were fed 1 liter of colostrum 4 h after birth and an additional liter 12 h later. Their absorption of the immunoglobulins A, G, and M, as indicated by serum concentrations, was equivalent at 16 and 24 h postpartum. Cortisol concentrations in serum at birth were high in both eutocial and dystocial calves and were correlated negatively with environmental temperatures prior to parturition. The dystocial calves had a lower cortisol concentration in serum at birth. The differences in cortisol concentrations between dystocial and eutocial calves and between experimental blocks influenced by environmental temperature could not be related to immunoglobulin absorption.

Failure to demonstrate transfer of milk prolactin into blood of milk-fed rats and calves

Possible absorption of ingested prolactin into blood of milk-fed neonates was studied in two species by different experimental approaches. In calves, secretion of endogenous prolactin was suppressed by administration of ergocryptine. Prolactin was measured in blood plasma at 20-min intervals before and after ingestion by the calves of bovine milk or colostrum which contained prolactin. Prolactin in plasma during the 2-h period after feeding was the same as that during the 1-h period before feeding. therefore, these data failed to demonstrate any absorption of ingested prolactin into the blood of neonatal calves. Previous research showed that bovine prolactin could be transferred into rat milk by injecting it into lactating rats. Blood serum was collected from rat pups that were suckling dams previously injected with bovine prolactin. Several dosages and times of administration were used in the experimental design, and blood serum also was collected from rat pups nursing control dams. All samples were immunoassayed for bovine prolactin with reagents that crossreacted only slightly with endogenous rat prolactin. Injection of lactating dams with bovine prolactin did not increase the amount of immunoreactive bovine prolactin in the sera of suckling rat pups. These results agree with those from the calf study and indicate that ingested bovine prolactin was not absorbed intact into the blood of neonatal rats.

The effects of corticosterone and cortisone on the uptake of polyvinyl pyrrolidone and the transmission of immunoglobulin G by the small intestine in young rats

1. The distribution of polyvinyl pyrrolidone along the intestinal lumen and in the intestinal wall, following oral administration to normal and corticosterone treated rats, was found to be extremely variable. Valid comparisons between the two groups of animals could not be made using this technique. 2. Three, 4 and 5 days after corticosterone treatment there was no significant change in the uptake of 125I-labelled polyvinyl pyrrolidone from standard doses injected into ligated segments of the distal small intestine; nor did the treatment induce precocious replacement of the absorptive cells in this region. Cortisone induced precocious cell replacement, a process which took up to 4 days to complete, and also led to a marked reduction in the uptake of 125I-labelled polyvinyl pyrrolidone from ligated segments of the distal intestine. 3. Three days after treatment with corticosterone (5 mg I.P. at 12 days) there was a marked reduction of labelled immunoglobulin G transport into the blood. Four and 5 days after treatment there was some recovery of the immunoglobulin G transport function. Three days after treatment with cortisone (5 mg I.P. at 12 days) there was closure of the gut to labelled immunoglobulin G. 4. The relevance of these results to antibody transmission and the termination of immunoglobulin transport is discussed.

The effects of cortisone acetate on stomach evacuation and the absorption of 125I-labelled globulins in young rats

1. After short exposure (3-5 hr) to I.P. cortisone acetate (5 mg), the reduced transmission of labelled globulin to the circulation in 14-day-old rats is due to the slow release of the oral dose from the stomach. The ability of the small intestine to absorb and transmit globulin to the circulation is comparable in control and experimental animals.2. About 26 hr after cortisone acetate treatment (5 mg), the greatly reduced absorption of labelled globulin from oral doses administered to rats aged 15 days is due to the combined effects of the slower release of the dose from the stomach and to changes which have occurred in the small intestine.3. About 50 hr after the administration of 5 mg cortisone acetate the effect on the rate of stomach evacuation is minimal in rats aged 16 days. When labelled globulin is introduced directly into the duodenum of these animals virtually no absorption occurs.4. The results obtained from the experiments in which labelled globulin was injected into the duodenum support the contention that the proximal half of the small intestine is an important site for macromolecular transport.

The influence of exogenous steroids on macromolecule uptake by the small intestine of the new-born rat

1. Plasma concentrations of cortisol and corticosterone measured by competitive protein binding in rats between 5 and 28 days after birth have been related to the intestinal uptake of [(125)I]polyvinyl pyrrolidone (PVP).2. Plasma cortisol concentration was consistently low throughout the period studied, but there was an increase in plasma corticosterone concentration at the time (18-21 days) when PVP uptake declined to zero (closure).3. Injection of a large dose of cortisone acetate 5 days after birth resulted in precocious closure; PVP uptake declined progressively to zero during the 6 days following the injection. Injection of this steroid at 12 days of age caused closure within 4 days.4. Precocious closure induced by cortisone acetate was closely comparable histologically with natural closure; the decline in PVP uptake was associated with the progressive displacement of vacuolated cells from the villi of the terminal intestine.5. Injection of corticosterone at either 5 or 12 days after birth also reduced PVP uptake. However, the reduction was transient and uptake returned to control levels some days after the injection.6. The temporary reduction in PVP uptake following corticosterone injection was not associated with any change in the histological appearance of the small intestine at the light microscope level.7. The injection of either cortisone acetate or corticosterone was followed by a period of impaired body growth and also a reduction of adrenal weight in animals injected at 12 days but not in animals injected at 5 days.

The effect of adrenalectomy or pharmacological inhibition of adrenocortical function on macromolecule uptake by the new-born rat intestine

1. Bilateral adrenalectomy in 18-day-old rats resulted in an extension by approximately 4 days of the period during which the villous epithelial cells of the small intestine took up polyvinyl pyrrolidone (PVP) of mean mol. wt. 160,000.2. The eventual termination of PVP uptake (;closure') closely resembled normal closure in control animals: the time course of the decline in uptake and the histological changes indicated that more mature ;PVP-impermeable' cells progressively ascended the villi.3. Injection of Metopirone was ineffective in animals 10 days after birth, but when injected after day 13 caused closure within 3 days.4. Metopirone injection significantly reduced the plasma concentration of corticosterone and caused a marked rise in the plasma concentration of deoxycorticosterone.5. Aminoglutethimide injection also produced precocious closure and had an effect similar to Metopirone on the plasma concentrations of corticosterone and deoxycorticosterone.6. Injection of Metopirone or aminoglutethimide increased the relative adrenal weight compared with control animals. Aminoglutethimide was more effective and caused approximately a 100% increase in adrenal weight.