ATP-sensitive K+ channels are composed of sulfonylurea receptor (SUR) and i
nward rectifier K+ channel subunit Kir6.2. Two subtypes of SUR have been id
entified: SUR1 constitutes the pancreatic beta-cell channel, while a recent
Northern blot analysis suggests the broad distribution of SUR2, which is m
ost intensely expressed in the ovary. Cellular distribution of SUR2 mRNA wa
s investigated by use of an in situ hybridization technique in several orga
ns, including the ovary, testis and adrenal gland, of adult rats. Intense a
nd selective expression of SUR2 mRNA was detected in sex hormone-producing
cells of the ovary, testis and adrenal gland. In the ovary, intense signals
for SUR2 mRNA were found in the theca folliculi (theca interna), corpus lu
teum, and interstitial gland. Leydig cells and the zona reticularis were se
lectively labeled in the testis and adrenal gland, respectively. Since mRNA
for Kir6.2 is absent or expressed at very low levels in the reproductive o
rgans and adrenal gland, a novel function for SUR, such as transport of ste
roids, is suggested in these organs.