K channels are important modulators of human corporal smooth muscle tone. The goals of this study were 3-fold: 1. to study the expression of the KATP channel in corporal tissue and cultured cells; 2. to determine if K channels are involved in the relaxation responses elicited by putative K channel modulators, & 3. to determine if K channel modulators alter intracellular calcium mobilization. Western blots and immunocytochemistry revealed abundant KATP channel expression in both frozen tissues and cultured cells. Cumulative concentration response curves (CRCs) were constructed for relaxation of PE-precontracted corporal tissue strips by Pinacidil (PIN), P1075, and U99751; which elicited relaxation responses with ≈EC50 values of of 3 nM, 60 nM, and 30 nM, respectively. Preincubation with glibenclamide (GLIB, 1 μM: 30 mins) partially inhibited the relaxation responses elicited by all of these putative K channel openers. Relaxation responses to P1075 were completely and immediately reversed by addition of KCl (60 mM), and more slowly, but completely by TEA (100 mM) or GLIB (1 μM). Calcium imaging experiments on fura-2 loaded cultured smooth muscle cells revealed that preincubation with (PIN) (1 μM) elicited a significant and completely GLIB-sensitive (10 μM) diminution in the peak amplitude of the ET-1 (endothelin-1)-induced intracellular calcium transient; which was equivalent to that observed in the presence of verapamil (1 μM), a L-type calcium channel blocker, or in the absence of extracellular calcium. These data strongly suggest the involvement of K channels (KATP) in this relaxation.
|Original language||English (US)|
|State||Published - 1997|
ASJC Scopus subject areas
- Molecular Biology