Glucagon increases urinary oxalate excretion in the guinea pig.
Holmes, Ross P., Chris H. Hurst, Dean G. Assimos, Harold O. Goodman.
Department of Urology, Bowman Gray School of Medicine, Wake Forest
University, Winston-Salem, NC 27157
APStracts 2:0085E, 1995.
Factors that influence hepatic oxalate synthesis are poorly defined.
Hormones are important regulators of hepatic metabolism and could
potentially be involved. The effects of hyperglucagonemia were
examined in guinea pigs injected with either saline or
pharmacological doses of glucagon for 4 days. Glucagon treatment
increased mean urinary oxalate excretion by 77% in male and 34% in
female animals. The levels of hepatic peroxisomal enzymes involved in
oxalate synthesis declined with glucagon treatment but experiments
with isolated peroxisomes indicated that oxalate synthesis in vitro
was unaffected. Glucagon decreased hepatic alanine levels 66%,
lactate 69%, and pyruvate 73%, but glycolate and glyoxylate levels
were unaffected. This decrease in alanine would substantially lower
the activity of alanine:glyoxylate aminotransferase activity in vivo
and make more glyoxylate available for oxalate synthesis. The
decrease in lactate and pyruvate concentrations would stimulate the
enzymatic conversion of glyoxylate to oxalate and may account for the
increase in oxalate synthesis without an increase in glyoxylate
concentration. These results demonstrate that hepatic oxalate
synthesis is influenced by metabolic changes and that alterations in
hepatic alanine, lactate and pyruvate concentrations may be important
elements.
Received 28 December 1994; accepted in final form 17 April 1995.
APS Manuscript Number E531-4.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 April 1995.