AJP - Endocrinology and Metabolism, Vol 263, Issue 2 E335-E339, Copyright © 1992 by American Physiological Society
Soluble and particulate phenylethanolamine N-methyltransferase in hypothalamus of diabetic rats
J. E. Chappell and J. K. Stewart
Department of Biology, Virginia Commonwealth University, Richmond 23284-2012.
Experimental diabetes increases total phenylethanolamine
N-methyltransferase (PNMT) activity in the medulla-pons but not in the
hypothalamus. In this study diabetes was induced with streptozotocin (65
mg/kg) in male Sprague-Dawley rats. Twenty-eight days after treatment there
were no differences in soluble PNMT activity in the hypothalamus of
diabetics and controls, but PNMT activity in a membrane-associated
(particulate) fraction of hypothalamus was evaluated approximately twofold
in tissues of diabetic animals compared with controls. A specific PNMT
inhibitor, incubated with tissue extracts of control rats, abolished
greater than 90% of particulate PNMT activity in the hypothalamus but
reduced soluble PNMT activity in the hypothalamus by only 47%. These
findings indicate that membrane-associated PNMT activity in rat
hypothalamus differs from soluble hypothalamic PNMT in the in vitro
response to an inhibitor and the in vivo response to diabetes and suggest
the importance of separating subcellular hypothalamic fractions prior to
assay of PNMT.
