Pkcm is the atypical protein kinase c isoform expressed by the immature ventricle. Rybin, Vitalyi O., Peter M. Buttrick, and Susan F. Steinberg. Departments of Medicine and Pharmacology, Columbia University, New York, New York and Department of Medicine, Albert Einstein College of Medicine, Bronx, New York
APStracts 3:0447H, 1996. (See corrigendum APStracts 4:0099H, 1997)
We recently identified a developmental decline in PKC isoform expression, at the level of the protein, in rat ventricular myocardium. To investigate mechanisms regulating PKC isoform expression in cardiac tissue, the present study uses Northern blot analysis to compare the abundance of PKC isoform mRNAs in neonatal and adult rat ventricular myocardium. PKC protein and mRNA were detected in both neonatal and adult rat ventricular myocardial preparations. In contrast, coordinate post-natal declines in the abundance of PKC and PKC proteins and transcripts were identified. An antiserum raised against the carboxyl-terminal sequence of PKCH detected abundant immunoreactivity in neonatal, but not adult, ventricular myocytes. However, PKCH transcripts were not detectable in the heart, either by Northern blot analysis or a reverse transcriptase-polymerase chain reaction approach, indicating that neither the myocytes nor the contaminating cellular elements in the heart express PKCH. Rather, PKCM, another atypical PKC isoform that is structurally highly homologous to PKCH, was detected at the protein and mRNA level in neonatal, but not adult, ventricular myocardium. Taken together, these results establish that developmental declines in calcium-sensitive, novel, and atypical PKC isoforms are paralleled by changes in the levels of the mRNAs encoding these proteins, suggesting transcriptional regulation of PKC during normal cardiac development. The results of this study further identify PKCM as the atypical PKC isoform expressed by the immature ventricle. 

Received 11 June 1996; accepted in final form 14 October 1996.
APS Manuscript Number H513-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996