Regulation of type II adenylyl cyclase mRNA in rabbit skeletal muscle by chronic motor nerve pacing.

Skeletal muscle exhibits a wide range in functional phenotype in response to changes in physiological demands. We have observed that, in response to changes in work patterns, alterations in gene expression of some proteins coincide with changes in adenylyl cyclase (AC) activity [Kraus, W.E., J.P. Longabaugh, and S. B. Liggett. Am. J. Physiol 263 (Endocrinol. Metab. 26): E266-E230, 1992]. We now examine AC isoform transcript prevalence in various rabbit skeletal muscles and in response to changing work demands. Using reverse transcriptase-polymerase chain reaction, we detected type II AC isoform transcripts in rabbit skeletal muscle. Ribonuclease protection analyses revealed that expression of the type II isoform significantly correlated with the percentage of fast-twitch type IIb/IId fibers (r2 = 0.765, P < 0.01). When a fast-twitch muscle was converted to a slow-twitch muscle via chronic electrical pacing, expression of type II AC mRNA significantly decreased. This response occurred 3 days after the onset of stimulation (78% decrease) and was still present after 21 days of stimulation (76% decrease). As type II AC is relatively insensitive to calcium regulation while sensitive to protein kinase C (PKC) signaling, these data provide further impetus for investigations of protein kinase A and PKC cross-talk signaling mechanisms in the regulation of gene expression.

Duke Scholars

Author William Erle Kraus Medicine, Cardiology