Down-regulation of lactogenic hormone receptors in Nb2 lymphoma cells by cholera toxin.

Exposure of lactogen-dependent (Nb2-11C) and lactogen independent (Nb2-SP) lymphoma cells to cholera toxin (0.05-50 pM) resulted within 18-28 h in a 50% decrease in the binding capacity of the intact cells to iodinated human growth hormone, and 40% decrease in cell-homogenates. Scatchard analysis revealed that the reduction in binding resulted from loss of cell-surface receptors accompanied by degradation of intracellular receptors.

Inhibition of casein and fat synthesis and alpha-lactalbumin secretion by progesterone in explants from bovine lactating mammary glands.

The effect of progesterone on casein and fat synthesis, on alpha-lactalbumin secretion and on accumulation of casein mRNA was studied in explants from bovine lactating mammary glands, cultured in the presence of insulin, cortisol or prolactin. All four biological activities were inhibited down to or below the level obtained in medium without prolactin. However, inhibition was only achieved by using concentrations of progesterone exceeding by 1000-fold those required for similar effects in tissue from non-lactating animals.

Partial purification and characterization of bovine mammary gland prolactin receptor.

Prolactin (PRL) receptors from the mammary gland of the lactating cow were solubilized with 3-[(3-cholamidopropyl)dimethylamonio]-1-propane sulfonate (CHAPS). Affinite chromatography on human growth hormone (hGH) coupled to Affi-Gel 10 resulted in over 500-fold purification, as compared to microsomal fractions. Scatchard analysis of the binding of hGH indicated an increase in the affinity constant of 2.

Characterization of lactogen receptors in lactogenic hormone-dependent and independent NB2 lymphoma cell lines.

A comparative study of lactogen receptors in lactogenic hormone-dependent (Nb2-11C) and independent (Nb2-SP) rat lymphoma cell lines revealed no significant differences in their binding and structural characteristics. The affinity for human growth hormone (hGH) and ovine prolactin is identical (Kd = 1.3 X 10(-10) M).

A comparative study of lactogenic hormone binding sites in the adrenal gland, ovary and kidney of the lactating cow.

The specific binding of 125I-oPRL to microsomal fractions from the adrenal gland, ovary and kidney of the lactating cow was significantly lower than binding of iodinated hGH. In addition, the ability of oPRL to compete with iodinated hGH as compared to hGH, was 50-fold lower in the adrenal gland 35-fold lower in the ovary and 18-fold lower in the kidney. These results are similar to those obtained in the mammary gland and liver, whereas the ability of oPRL to compete with iodinated hGH was 90-fold lower, as compared to hGH.

A model for in vitro proliferation of undifferentiated bovine mammary epithelial cells.

A method for culturing bovine undifferentiated mammary epithelial cells embedded in collagen gels is described. Cell growth was quantitated by incorporation of tritiated thymidine. Maximal rate of incorporation was achieved in media supplemented with sera, however considerable growth was observed in serum-free medium supplemented with insulin, transferrin and selenium.

Human growth hormone-stimulated mitogenesis of Nb2 node lymphoma cells is not mediated by an immediate acceleration of phosphoinositide metabolism.

Lactogenic hormones stimulate the mitogenesis of Nb2-11C rat lymphoma cells and this stimulation is enhanced by 12-O-tetradecanoyl phorbol ester (TPA). The effect of human growth hormone (hGH) and TPA on phosphoinositide metabolism in Nb2-11C cells was tested by measuring the incorporation of [3H]myo-inositol or 32P or measuring the breakdown of polyphosphoinositides in cells prelabeled with [3H]myo-inositol, 32P or [3H]arachidonic acid. We found that none of these processes is immediately stimulated by either hGH and/or TPA.

Short-term regulation of prolactin receptors in the liver, mammary gland and kidney of pregnant and lactating rats infused with ovine prolactin or human growth hormone.

Short-term regulation of prolactin (PRL) receptors was studied in ketamine-anaesthetized 18-day pregnant or 7-day lactating female rats, by infusing them with various doses of oPRL or human growth hormone (hGH) for 0-3 h and measuring the binding of [125I]oPRL of [125I]hGH to the microsomal fractions prepared from the liver, mammary gland and kidneys of animals sacrificed at various states of infusion. Our main findings are: In pregnant rats, only 30% of liver receptors are unoccupied and infusion with 25 micrograms/h for 3 h of either oPRL of hGH decreased both free and total receptors by 22-30% while infusion with 250 micrograms/ml caused an additional decrease only in the free receptors. In the mammary gland and the kidney of pregnant rats, all receptors seem to be unoccupied; infusion with 25 micrograms/ml had none or a slight elevating effect on the number of both free and total receptors in the mammary gland but caused a significant 3-fold increase in the kidney; infusion with 250 micrograms/ml, however, resulted in a slight decrease in the mammary gland and a significant decrease in the kidney in both total and free receptors.

Partial amino acid sequence of porcine elastase II. Active site and the activation peptide regions.

The partial amino acid sequence of porcine elastase II, isolated from crude trypsin Type II, was determined. The enzyme consists of two polypeptide chains, a light chain composed of 11 residues, and a heavy chain (Mr = 23 500) with four intrachain disulfide bridges; the two chains are held together by one interchain disulfide bond. Elastase II was fragmented into several peptides by chemical cleavages with CNBr at the two methionine residues, 99 and 180 (chymotrypsinogen numbering), and with hydroxylamine at the peptide bond following DIP-Ser195.

Inhibition of lactogenic activities of ovine prolactin and human growth hormone (hGH) by a novel form of a modified recombinant hGH.

A recombinant analog of human GH (hGH) lacking 13 amino acids at the amino-terminus (Met14hGH) inhibited the hGH- or ovine PRL (oPRL)-stimulated proliferation of Nb2 lymphoma cells and bovine PRL-stimulated fat synthesis and alpha-lactalbumin secretion in explants from bovine lactating mammary gland. The inhibition was competitive in nature, and in Nb2 cells could be abolished by an excess of hGH or oPRL. Inhibition of oPRL-stimulated proliferation of Nb2 cells by Met14hGH could also be specifically abolished by anti-hGH monoclonal antibodies.

Enhancement of human growth hormone-stimulated mitogenesis of Nb2 node lymphoma cells by 12-O-tetradecanoyl-phorbol-13-acetate.

The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) enhanced human (h) GH- and ovine PRL-stimulated mitogenesis of the Nb2-11C clone of rat lymphoma cells. Maximal enhancement of 25% in the proliferation rate was achieved with 20 nM TPA. The enhancing effect was found at all levels of hGH (0.

The fate of [125I]-labeled human leukocyte-derived alpha interferon in the rat.

In order to follow the catabolic fate of interferon in the body, [125I]-labeled human alpha interferon was infused into rats. Interferon activity and TCA-precipitable radioactivity in the blood reached a steady state after 60 min of infusion, while TCA-soluble radioactivity continued to increase during the entire infusion period. A massive accumulation of both active interferon and degradation products of interferon were found in the kidney at the end of the infusion.

Digestion of elastin by porcine pancreatic elastase I and elastase II.

Elastin was fully solubilized by digestion with elastase I or elastase II. Each digest was separated into high-molecular weight and low-molecular weight fractions that were characterized by the correspondence to their amino acid content, N-terminal sequence and C-terminal amino acids. It was found that although the relative amount of amino acids in the low-molecular weight fraction obtained by digestion with elastase I was lower than in digestion with elastase II, no major difference in the type of bonds cleaved in the low- or high-molecular weight fractions of each digest could be seen.

Binding sites of human growth hormone and ovine and bovine prolactins in the mammary gland and the liver of lactating dairy cow.

Membrane preparations and Triton X-100 solubilized fractions from the mammary gland and liver of the lactating dairy cow were capable of specific binding of [125I]hGH and [125I]oPRL. The specific binding of the latter was significantly lower and could not be increased by higher receptor levels. Displacement studies of [125I]hGh by hGH, bPRL and oPRL revealed that the two latter hormones have a 20-40-fold lower affinity for the receptor than hGH, although strong indications exist that they all bind or the same sites.

Human growth hormone but not ovine or bovine growth hormones exhibits galactopoietic prolactin-like activity in organ culture from bovine lactating mammary gland.

Explants from the mammary gland of 6 lactating cows were cultured in M-199 medium containing insulin (1.0 micrograms/ml) and hydrocortisone (0.5 micrograms/ml) and supplemented with bPRL (0.

Down-regulation of prolactin receptors in the liver, mammary gland and kidney of female virgin rat, infused with ovine prolactin or human growth hormone.

Down regulation of prolactin (PRL) receptors resulting from i.v. infusion of oPRL or human growth hormone (hGH) into female virgin rats was demonstrated.

Hormonal control of casein synthesis in organ culture of the bovine lactating mammary gland.

Explants from lactating bovine mammary gland were cultured in vitro in serum-free medium though 1-9 d. casein synthesis was determined by [32P] incorporation into newly synthesized Ca rennin precipitable fraction. High correlation (r = 0.

The effect of dietary raw and autoclaved soya-bean protein fractions on growth, pancreatic enlargement and pancreatic enzymes in rats.

1. Raw soya-bean meal (RS) was fractionated into soya-bean lyophilized extract (SLE), soya-bean lyophilized residue (SLR), acid-precipitated proteins (APP) and whey proteins. 2.

Involvement of the kidney in catabolism of human leukocyte interferon.

The metabolic fate of human leukocyte interferon (HuIFN-alpha) was studied after intravenous injection into rats and cynomolgus monkeys. At various intervals the animals were sacrificed and the HuIFN-alpha content determined in serum and various tissues. HuIFN-alpha quickly disappeared from the circulation and was found mainly in the kidneys, in which levels were at least 7- to 10-fold higher than in the liver, spleen, lungs, heart, brain and muscles.

The kidney is the main site of interferon degradation.

Male Sprague Dawley rats (300 g) were infused by constant infusion into the jugular vein through 3-5 h with human leukocyte-derived interferon (HuIFN-alpha 10(6) units/h, 0.9 ml/h). Blood samples were collected every 20 min through the carotid.