Leptin receptors in the adrenal medulla of the rat.
Cao, Gao-Yuan, Robert V. Considine, Richard B. Lynn.
Dept. of Medicine, Jefferson Medical College, Thomas Jefferson
University, Philadelphia, PA 19107
APStracts 4:0116E, 1997.
Leptin is the protein product of the recently cloned obesity gene.
Leptin receptor mRNA is found in a number of central and peripheral
locations. The hypothalamus is a presumed site of action. However,
little is known about the specific locations of the receptor in
peripheral organs. Epinephrine has potent anorectic effects and can
cause weight loss by a variety of mechanisms. Excretion of
epinephrine is reduced in the ob/ob mouse which lacks leptin,
suggesting an effect by leptin on the adrenal medulla. In the current
study, the presence of the leptin receptor was identified on
epinephrine secreting cells in the adrenal medulla.
Immunohistochemical studies found dense leptin receptor-like
immunoreactivity in the adrenal medulla with no labeling in the
adrenal cortex. Double immunofluorescent labeling confirmed that the
leptin receptor was present on cells that were PNMT-like
immunoreactive and therefore were epinephrine secreting cells. Leptin
receptor mRNA in the adrenal medulla was detected by RT-PCR with the
majority of the mRNA coding for the short isoform (Ob-Ra) of the
receptor. Finally, autoradiography was performed using [125I]leptin
and found specific binding in the adrenal medulla with no specific
binding in the adrenal cortex. These results suggest that leptin may
have a direct effect on epinephrine secreting cells in the adrenal
medulla. Epinephrine may play a role in mediating the effects of
leptin to reduce body weight.
Received 25 March 1997; accepted in final form 20 May 1997.
APS Manuscript Number E136-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 11 June 1997