Leptin receptors in the adrenal medulla of the rat.
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 phenylethanolamine N-methyltransferase-like immunoreactive and therefore were epinephrine-secreting cells. Leptin receptor mRNA in the adrenal medulla was detected by reverse transcriptase-polymerase chain reaction, with the majority of the mRNA coding for the short isoform (Ob-Ra) of the receptor. Finally, autoradiography was performed using 125I-labeled leptin; specific binding was found 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.
Cao
G Y
GY
Department of Medicine, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Considine
R V
RV
Lynn
R B
RB
D000313:Adrenal Medulla / Q000378:metabolism*; D000818:Animals; D001345:Autoradiography; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin
D002352:Carrier Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; C515447:leptin receptor, mouse