Effect Of Exogenous Prolactin Research Articles

Daily variations in response of certain immunity indices to prolactin in White Leghorn chickens.

The purpose of this experiment was to elucidate whether the effect of exogenous prolactin (PRL) on immunity parameters of White Leghorn chickens varies during the day. The experiment was carried out on cockerels kept after hatching during 6 weeks under L:D = 12:12 conditions. During 5 consecutive days cockerels were injected with bovine PRL (150 micrograms per bird daily) or its solvent at different time points, i.e., at 0, 4, 8 or 12 HALO (Hours After Light Onset). The birds were sacrificed 24 hours after the last injection at the same time point when the injections were given. It was found that given at 4 HALO prolactin raised, whereas at 8 HALO it decreased the peripheral lymphocyte number. PRL had no effect on granulocyte number, natural anti-rabbit red blood cells (anti-RRBC) agglutinin titre and serum lysozyme activity. Administered at 0 and 12 HALO PRL tended to decrease the thymus and bursa of Fabricius weight. This different PRL effect on peripheral lymphocytes in chickens during the circadian period may be one of the causes of varying effect of this hormone on immunity (stimulatory or suppressive) described in literature. The role of PRL in regulation of immunity is discussed in relation to the possibility of PRL receptors occurrence on chickens lymphocytes.

Lipid metabolism indices and plasma corticosterone concentration in chickens treated with prolactin at different time points.

The effect of exogenous prolactin (PRL) on the weight and lipid content of the liver and abdominal adipose tissue as well as on the concentrations of total lipids and lipoprotein fractions (portomicrons, VLDL, LDL, HDL) in plasma was investigated in chickens. PRL or its solvent were administered at different time points (0, 4, 8, and 12 hours after light onset = HALO) during 5 consecutive days. The birds were exsanguinated at the same time of the day when they received the injections, 24 hours after the last one. At the same time plasma corticosterone (CS) concentration was determined in these chickens and also during 24 hours in intact chickens matched for age. PRL affected fat accumulation in the experimental birds and the intensity of this effect depends on the time of the day at which it was administered. PRL caused rise of the weight of the fat tissue and its lipid content when it was injected at 8 or 12 HALO. This was associated with a significant increase of total plasma lipids and with an insignificant increase in the level of lipoprotein fractions excluding portomicrons. PRL increased also (at 4 HALO) or decreased (at 8 HALO) the liver weight. Handling of the birds during vehicle injections decreased the corticosterone level in the control chickens as compared with the intact ones; PRL raised the level of CS at 0 HALO significantly. The role of PRL in the intensification of fat transport is discussed.

The effect of exogenous prolactin on lactation performance of first-litter sows given protein-deficient diets during the first pregnancy

Twenty-four sows were used to study the effects of dietary protein restriction during pregnancy and exogenous porcine prolactin (pPRL) during late pregnancy and throughout lactation on lactation performance. Eight sows were given a protein-adequate diet containing 179 g crude protein (CP)kg−1 during their first pregnancy while the remaining 16 sows received the same amount of a diet containing 80 g CP kg−1. Eight of the sows given 80 g CP kg−1 during pregnancy were injected with 15 mg pPRL i.m. twice daily at 08:00 and 20:00 between day (d) 102.1 (±0.3) of pregnancy and weaning after their first lactation. Pregnant sows offered the low protein diet gained significantly less body weight during gestation and tended to eat less in the subsequent lactation than sows given the protein-adequate diet. Dietary protein had no significant effect on birth weight, milk yield, milk composition or growth rate of the litter during lactation. Neither dietary protein intake during pregnancy nor exogenous prolactin affected the concentrations of plasma glucose, serum insulin, urea or non-esterified fatty acid (NEFA) during lactation. The concentration of lactose in plasma during lactation was unaffected by treatment, but at d 105 of pregnancy, plasma lactose levels were greater in sows which had received exogenous prolactin (32.4 vs. 6.2 mg l−1, P < 0.05). The concentrations of RNA and DNA in mammary tissue biopsies were unaffected by either dietary protein or pPRL. The concentration of RNA and DNA increased between d 70 and 90 from 0.66 to 2.77 mg g−1 and from 0.54 to 1.19 mg g−1, respectively. Thereafter, RNA increased to 4.40 mg g−1 at d 14 of lactation whilst DNA concentration remained at a similar level of 0.90 mg g−1. Milk yield of sows between d 5 and 8 and between d 19 and 22 of lactation was reduced from 8.36 to 7.00 kg day−1 and from 10.74 to 8.22 kg day−1, respectively, in sows given pPRL. The protein content of colostrum from sows treated with pPRL was reduced from 164 to 104 g kg−1 whereas the fat content increased from 47 to 127 g kg−1. These results indicate that the administration of exogenous pPRL during late pregnancy and throughout lactation initiated lactogenesis prematurely and reduced subsequent milk yield during established lactation.

Interactions of Human Growth Hormone and Prolactin on Pituitary and Leydig Cell Function in Adult Transgenic Mice Expressing the Human Growth Hormone Gene1

Adult male transgenic mice expressing the human growth hormone (hGH) gene are hypoprolactinemic. To evaluate the effects of exogenous prolactin (PRL) and endogenously secreted hGH on pituitary and Leydig cell function, adult male transgenic and nontransgenic mice (10-16 wk of age) were treated s.c. with either saline-polyvinylpyrrolidone (PVP) or oPRL (100 micrograms/mouse) in saline-PVP. Animals were treated twice daily; a total of 7 injections were given. One hour after the last injection, each group of mice was treated i.p. either with saline or oLH (0.3 microgram/g BW); 2 h later, blood was obtained via heart puncture. Plasma FSH, LH, PRL, androstenedione (A-dione), and testosterone (T) levels were measured by validated RIAs. Basal PRL levels were significantly lower (p less than 0.001) and basal LH concentrations were significantly higher (p less than 0.01) in transgenic than in nontransgenic mice. Administration of PRL significantly decreased (p less than 0.01) plasma LH levels in transgenic mice, whereas similar treatment of nontransgenic mice increased (p less than 0.01) circulating LH concentrations. Plasma FSH levels were unaffected in transgenic and nontransgenic mice treated with saline or PRL. Basal plasma A-dione and T levels were similar in both groups of animals and were significantly increased after treatment with LH. Administration of PRL increased T levels in transgenic and nontransgenic mice, but the T response to LH treatment was greater in PRL-treated transgenic mice, indicating the synergistic effect of hGH in the biosynthesis of T.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of prolactin on tolerance and dependence to acute administration of morphine

The effect of exogenous prolactin on the development of acute tolerance to and dependence on morphine was studied. As described elsewhere, analgesia induced by prolactin was subject to tolerance. Pretreatment with prolactin enhanced the development of tolerance to analgesia induced by morphine while it effectively suppressed the withdrawal symptoms. These results indicate that prolactin behaves like an opioid agonist and suggest that it may have therapeutic implications in the management of opioid dependence.

Effect of exogenous prolactin on immunity in chickens

The effect of exogenous prolactin on the number of peripheral white blood cells (WBC), anti-sheep red blood cell (anti-sheep RBC) and anti-rabbit red blood cell (anti-rabbit RBC) agglutinins was investigated in White Leghorn cockerels immunised twice with sheep RBC. It was found that prolactin, when administered for five days after second immunisation, raised production of anti-sheep RBC antibodies and lymphocyte number in comparison with the control group given injections of the solvent. Repeated injections of the solvent resulted in statistically significant differences in the number of granulocytes and lymphocytes.

Effects of exogenous prolactin on ovarian growth and fattening in the redheaded bunting, Emberiza bruniceps

Subcutaneous daily injections of ovine prolactin (PRL) inhibit photoperiodic induction of gonads and fattening in the female redheaded bunting ( Emberiza bruniceps). However, birds respond to the same photoperiod (15L:9D) after withdrawal of the exogenous PRL. Further, PRL injections given in late hours during the subjective days induce ovarian regression in the photostimulated females. The results suggest that the PRL has an inhibitory role on gonadal photoperiodic responses in redheaded buntings, and extend our understanding of the regulatory function of PRL in migratory birds.

Effect of exogenous prolactin on peripheral luteinizing hormone levels in ovariectomized cows.

Effect of exogenous prolactin on peripheral luteinizing hormone levels in ovariectomized cows.

Correction of developmental defects in adrenal steroid metabolizing enzymes of the genetically male rat pseudohermaphrodite by prolactin

The effects of exogenous prolactin alone and with testosterone propionate on the activity of adrenal enzymes metabolizing androstenedione and testosterone were determined in genetically androgen-insensitive pseudohermaphrodites and their littermate males and females at 60 days of age and in adult pseudohermaphrodites. A significant correction of the elevation of both steroid 5α-reductase and 3β-hydroxysteroid oxidoreductase was produced in rat pseudohermaphrodites by prolactin at all ages. This correction was enhanced by the addition of testosterone propionate only in the pubertal pseudohermaphrodites. These treatments also lowered both enzymatic activities in males and females at 60 days of age. The results indicate that the adrenal enzyme defects occurring in this genetic model of prepubertal castration, the pseudohermaphrodite, is corrected by prolactin. Moreover, it appears that prolactin may be involved in the pubertal differentiation of the normal adrenal.

Branchial sodium exchange in seawater-adapted Tilapia mossambica: effects of prolactin and hypophysectomy.

The effects of exogenous prolactin and hypophysectomy were tested on Na exchange across the gills of Tilapia mossambica adapted to sea-water. Exogenous prolactin produced a 75% decrease of both total Na influx and Na efflux. Total Na influx was measured simultaneously with the drinking rate. Water ingestion stopped almost completely in prolactin-treated fish. Thus branchial net excretion flux of Na was reduced 75% by prolactin. Hypophysectomy produced a 50% inhibition of Na efflux across the gill.

Milking-induced release of endogenous prolactin in cows infused with exogenous prolactin.

SummaryExogenous prolactin (3 or 9 mg NIH–B3/hr) or saline was infused for 2.5 hr into 6 cows. The prolactin or saline infusions were repeated on alternate days for a total of 4 days. Approximately 45 min was required to achieve a stable baseline after the prolactin infusion was started. The exogenous prolactin, which increased serum prolactin approximately 5– and 8–fold above baseline endogenous concentrations, did not prevent the release of endogenous prolactin in response to milking. When the infusion was stopped serum prolactin disappeared with a 1/2 time of 23–25 min. We conclude that the inhibitory effects of exogenous prolactin previously reported on endogenous prolactin secretion must be exerted primarily on synthesis rather than release mechanisms, or the animals may require chronic exposure to high concentrations of prolactin.The able technical assistance of Mrs. Annemieke Ambrosier is gratefully acknowledged.

Effects of exogenous prolactin on reproduction and growth in adult males of the lizard Anolis carolinensis

Adult male Anolis were treated with 5–150 μg/day of exogenous ovine prolactin during the winter and spring under several different conditions of light and temperature. Calorimetric assays of various food insects were used to determine caloric assimilation rates. Prolactin increased food consumption markedly in the winter, when appetites were normally low, and promoted an increase in lean body weight, while fat depots in liver and abdominal fat pads were reduced. Thyroid epithelia were hypertrophied but metabolism was reduced with prolactin. Growth hormone in a dose (1 μg/day) equivalent to the maximum contamination expected in the prolactin preparation had no effect on the growth of Anolis. The natural increases in appetite during the spring obviated the action of prolactin on food consumption, but the hormone continued to exert a somatotropic effect. Prolactin-treated animals stored significantly less fat than controls. Increased body length occurred in prolactin-treated animals maintained on fluctuating temperatures (32-20°C) while the controls only fattened. Prolactin-treated lizards exposed to 32°C continuously did not grow in length but molted more frequently. Thyroid histology and metabolism were unaffected by prolactin during the spring. There was no effect of prolactin on the testes, during recrudescence in the winter or when fully active in the spring. Sexual behavior and accessory sex organs were also unaffected by prolactin, whereas 1 μg growth hormone stimulated accessory sexual structures.