The Stimulation of Liver Phosphorylase b by AMP, Fluoride and Sulfate. A Technical Note on the Specific Determination of the a and b Forms of Liver Glycogen Phosphorylase

Methods for obtaining and processing rat liver for determination of glycogen phosphorylase a and synthase I activity were studied. An extremely rapid and profound increase in phosphorylase was induced by hypoxia. The effect on synthase I was slower and less striking. Using alpha- and beta-adrenergic antagonists, a catecholamine-depleting agent, and a ganglionic blocking agent, it was determined that adrenergic stimulation secondary to the surgical procedure required to obtain the liver was not a significant factor. The anesthetic agent used also had a significant effect on the proportion of phosphorylase in the a form. Seconal anesthesia resulted in lower phosphorylase a levels than did ether or urethan anesthesia.

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Determination of mitochondrial calcium content in hepatocytes by a rapid cellular fractionation technique. Vasopressin stimulates mitochondrial Ca2+ uptake

Biochemical Journal ◽

10.1042/bj2200417 ◽

1984 ◽

Vol 220 (2) ◽

pp. 417-421 ◽

Cited By ~ 21

Author(s):

S B Shears ◽

C J Kirk

Keyword(s):

Glycogen Phosphorylase ◽

Calcium Content ◽

Transient Increase ◽

Mitochondrial Calcium ◽

Phosphorylase Activity ◽

Hormone Stimulation ◽

Control Value ◽

Glycogen Phosphorylase Activity ◽

Stimulation Of

Stimulation of hepatocytes with vasopressin (10 nM) in the presence of 1.25 mM extracellular Ca2+ increased glycogen phosphorylase activity 4-fold within 15s and provoked a rapid efflux of cell-associated Ca2+. Vasopressin also caused a transient increase in the Ca content of a mitochondria-rich fraction separated within seconds of hormone stimulation by a rapid fractionation technique [Shears & Kirk (1984) Biochem. J. 219, 375-382]. The Ca content of this fraction was restored to the control value within 2 min of hormone addition. These results indicate that mitochondria are not the source of the cell-associated Ca which is mobilized in the cytosol of vasopressin-stimulated hepatocytes. Rather, these organelles buffer the increase in cytosol [Ca2+] attributable to Ca mobilization from non-mitochondrial sources.

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ADENOHYPOPHYSEAL LH CONTENT IN NORMAL, ANDROGEN-STERILIZED AND PROGESTERONE-PRIMED STERILE FEMALE RATS

Acta Endocrinologica ◽

10.1530/acta.0.0390013 ◽

1962 ◽

Vol 39 (1) ◽

pp. 13-21 ◽

Cited By ~ 19

Author(s):

Roger A. Gorski ◽

Charles A. Barraclough

Keyword(s):

Ascorbic Acid ◽

Electrical Stimulation ◽

Quantitative Determination ◽

Median Eminence ◽

Hypothalamic Stimulation ◽

Female Rats ◽

Rat Pituitary ◽

Gland Content ◽

Stimulation Of

ABSTRACT We have previously suggested that the failure of the androgen-sterilized, persistent-oestrous rat to ovulate, following electrical stimulation of the median eminence structures of the hypothalamus, is due to an insufficiency in adenohypophyseal LH concentration. Using the ovarian ascorbic acid technique for quantitative determination of pituitary LH content, the present studies have demonstrated that the sterile rat pituitary gland contains one-third the LH content of the normal prooestrous gland. Furthermore, not only does progesterone priming of this persistent-oestrous rat result in a 75 % increase in LH concentration, but on hypothalamic stimulation sufficient LH is released to induce ovulation. The decrease in LH concentration which accompanies ovulation in the progesterone-primed, sterile rat is approximately 45 % of the total gland content as compared with a 51 % decrease in pituitary content in the normal cyclic rat.

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