Conformation of equine pituitary somatotropin

Equine pituitary somatotropin (growth hormone) has been studied by zero-order and second-order absorption spectroscopy, and by circular dichroism. Difference absorption spectra have also been generated during proteolytic digestion of the hormone. The molar extinction coefficient of the native protein was found to be 16,050 +/- 330 M-1 cm-1 at 278.1 nm. Comparison of the conformations of equine somatotropin and somatotropins isolated from several other mammalian species indicates a close structural relationship between these molecules. With the increasing number of species which have been studied, it is becoming evident that with regard to conformation, the somatotropins can be subdivided into at least three major groups.     

Conformation of sturgeon pituitary somatotropin

Pituitary somatotropin (growth hormone) from the sturgeon (Acipenser gulden-stadti) has been studied by zero-order and second-order absorption spectroscopy, as well as by circular dichroism. Difference absorption spectra have also been generated during proteolytic digestion of the hormone. The molar extinction coefficient of the native protein was found to be 15,000 +/- 110 M-1 cm-1 at 278.5 nm. Comparison of the conformations of sturgeon somatotropin and somatotropins isolated from several mammalian species, including bovine and human, indicates a close relationship between these molecules. Such similarities may be related to the relatively high biopotency of this fish hormone in mammalian assay systems.     

The conformation of monkey pituitary somatotropin

Monkey pituitary somatotropin has been studied by zero-order, second-order, and circular dichroism spectroscopy. Difference absorption spectra have also been generated during proteolytic digestion of the hormone. The molar extinction coefficient of the native protein was found to be 23,800 +/- 550 (M-1 cm-1) at 276.6 nm. A comparison of the conformations of monkey and human pituitary somatotropins indicates a close relationship between the two molecules, including alpha-helix contents of 55 +/- 5%.     

Colchicine alters lactate utilization in isolated hepatocytes of rats treated with CCl4 and ethanol

Lactic acidosis has been described in patients with liver disease. Hyperlactacidaemia results from an imbalance in lactate production versus lactate utilization. It is estimated that the liver utilizes approximately 30 percent of the total lactate produced in the body under basal conditions, primarily by gluconeogenesis. The gluconeogenesis from lactate 10 mM and lactacidaemia were determined in order to investigate the effects of CCl₄+ethanol administration in liver injury and, the possible effect of colchicine in our experimental fibrosis model. The tests were determined after 15, 30 or 45 days of treatment. The results indicate that the gluconeogenesis was significantly inhibited in both CCl₄+ethanol groups and CCl₄+ethanol+colchicine groups. By contrast, the lactacidaemia levels were much higher in the CCl₄+ethanol groups than the colchicine groups. Summarising, we have documented that hyperlactacidaemia is due to the inhibition of lactate utilization by the isolated hepatocytes in experimental cirrhosis, and that the improvement in lactacidaemia caused by colchicine is not primarily due to an increase in hepatic lactate utilization.     

Purification and characterization of pituitary bovine somatotropin

Bovine somatotropin (bST) has been isolated from pituitary glands and compared in a variety of chemical analyses and bioassays with somatotropin derived from recombinant Escherichia coli. Comparison of pituitary extracts and purified bST by Western blot analysis of two-dimensional gels suggested that the immunoreactive somatotropin species present in the extract were also present in the purified material, with no significant losses or degradation as a result of the purification method. NH2-terminal sequence analysis indicated the presence of equal quantities of Ala-Phe-Pro-Ala-Met-Ser-Leu-Ser- and Phe-Pro-Ala-Met-Ser-Leu-Ser- sequences. The Met-Ser-Leu-Ser-NH2-terminal sequence, a degradation product observed in NIH standard lots, was not detected. Assay of bioactivity in a bovine liver receptor-binding assay and in a female rat growth assay showed pituitary bST and recombinant methionyl-bovine somatotropin to be equipotent. Tryptic maps and sequence analysis of pituitary-derived somatotropin suggest the presence of isoaspartate derivatization at Asp128.     

Gonadotropin levels in sera and pituitary glands of female rats treated with alloxan

Alloxan monohydrate in saline solution was injected intraperitoneally into young (35 day old) and older (95 day old) female rats at dose levels of 7.5 mg or 15.0 mg/100 g of body wt. In both age groups of rats, only the high dose of alloxan was effective to produce permanent diabetes as judged by the presence of hyperglycemia and glucosuria. The rats were bled by cardiac puncture and autopsied 21 days following the alloxan treatment. In young rats, diabetes resulted in a significant reduction in body weight gain and in ovarian and anterior pituitary weights. Serum and pituitary LH levels of these young diabetics were, respectively, significantly lower and essentially the same, whereas their serum and pituitary FSH levels were, respectively, essentially the same and significantly higher than those of the controls. In the older diabetics, although a significant decrease in body weight gain was observed, the ovarian and pituitary weights as well as the serum and pituitary gonadotropin levels were essentially the same as compared to the controls.     

The effect of somatotropin on adenosine deaminase activity in tissues of rats with hypo- and hyperthyroidism

It has been shown that under hypothyrosis (thyroidectomy) the adenosine deaminase activity in the total suspension of thymocytes does not change as compared with that of intact rats. When suspension of thymocytes was separated by centrifugation in the ficoll-urografin density gradient into 6 fractions the enzyme activity has been found to increase by 83 and 31%, respectively, in light fractions with the ficoll density of 1.065 and 1.071 and to decrease by 21% in the fraction with density of 1.095 as compared with the intact rats. The enzyme activity in spleen homogenate of hypothyroid rats is higher by 72% than the norm. This activity in thymocytes and spleen of hyperthyroid rats is lower by 37% and 30% respectively. Somatotropin administration to rats normalizes these changes.     

Hyperglycemic effect of prolactin in anterior pituitary transplanted rats

The role of prolactin as a diabetogenic hormone was based on studies describing the ability of administered prolactin to raise the level of serum glucose. In the present study, female rats were made hyperprolactinemic by the transplantation of two anterior pituitary glands under the renal capsule, obtained from littermate donors. Chronic hyperprolactinemia increased blood glucose and impaired the glycolytic pathway of hepatic carbohydrate metabolism. However, basal serum insulin values were not different from those of controls. These data suggest that chronic hyperprolactinemia has an hyperglycemic effect and has a significant influence on glucose handling by the liver, through reduced glycolysis.