C. Deminteguiaga et al., BETA-2-ADRENERGIC BUT NOT VASOPRESSIN V2 RECEPTOR MESSENGER-RNAS ARE EXPRESSED IN THE STRIA VASCULARIS OF THE RAT INNER-EAR, Pflugers Archiv, 436(6), 1998, pp. 940-947
Activation of beta 2-adrenergic receptors (beta 2-AR) and of V2-vasopr
essin receptors (V2-VR) has been shown to stimulate cAMP production in
the stria vascularis. Expression of these receptors in this epithelia
l structure has never been investigated at the mRNA level. A quantitat
ive assay based on the reverse transcriptase-polymerase chain reaction
(RT-PCR) method was developed to study the expression of beta 2-AR, v
asopressin (V1a,V1b,V2) and oxytocin receptors in rat microdissected s
tria vascularis fragments. Steady-state mRNA levels were measured usin
g mutant cRNAs as internal standards. We consistently Found evidence o
f the expression of beta 2-AR transcripts in the stria vascularis: how
ever, no such evidence of V2-VR mRNA expression was found in studies o
f the same samples. As our method is sensitive enough to detect 200 mR
NA molecules, V2-VR mRNA is thought to be present, if at all, at a con
centration that is 40 times lower than that of the beta 2-AR transcrip
ts. V1a-VR mRNA was found to be present in trace amounts and is the on
ly subtype of the vasopressin-oxytocin receptor family expressed in th
is epithelium. These data demonstrate, at the mRNA level, the expressi
on of beta 2-AR in the stria vascularis. and indicate that V2-VR trans
cripts are not present in this structure.