Important electrophysiological, pharmacological, and biochemical changes occur in myocardial cells during development of the heart, which obviously affect its functional properties. The identity and properties of the currents in young embryonic animals is not well understood. Young embryonic chick hearts have slowly-rising, Na-dependent, TTX-insensitive action potentials. The number of fast Na channels increases during development so that the old embryonic chick heart has a typical fast-rising Na-dependent action potential. Thus, the types and number of channels changes during development. Channel properties and kinetics may also change during development (e.g., K channels display less inward-rectification in young vs. old embryonic chick hearts). The identity and properties of the various cardiac channels will be examined at different stages of development, including changes in the Na channels using photoaffinity probes of tetrodotoxin. In these studies, whole-cell voltage clamp and patch clamp techniques will be used in single cells of embryonic chick hearts at different stages of development. In the adult heart, cAMP-dependent phosphorylation regulates the function of slow Ca channels (and perhaps other channels). Phosphorylation by other protein kinases may also regulate channel function. For example, cGMP-, calmodulin- and phospholipid-dependent phosphorylation have all been implicated in slow channel function. However, the role of protein phosphorylation in the regulation of channels during development is unknown. The proposed experiments seek to determine the role of protein phosphorylation during development of the embryonic chick heart. Changes in cAMP levels occur during development; whether cGMP levels also change is not known. Calmodulin levels, cGMP levels and various protein kinase activities will be measured at different stages of development. Regulation of sarcolemmal proteins various protein kinases will be examined to determine whether the pattern of phosphorylation changes during development, as has been shown for cAMP- dependent phosphorylation. The role of dephosphorylation will also be examined electrophysiologically and biochemically. To identify and further study the Ca channel protein(s) during development, a specific covalent affinity reagent, (3H)nifedipine isothiocyanate will be used to label the channel. Biochemical and electrophysiological experiments will be correlated to give a better understanding of channel properties and function during development. These studies are improtant, since the response of the heart to pathological conditions (e.g., myocardial ischemia) and to cardioactive drugs is largely determined by the types and properties of channels present.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL031942-06
Application #
3343117
Study Section
Cardiovascular Study Section (CVA)
Project Start
1983-07-01
Project End
1991-11-30
Budget Start
1987-12-01
Budget End
1988-11-30
Support Year
6
Fiscal Year
1988
Total Cost
Indirect Cost
Name
University of Cincinnati
Department
Type
Schools of Medicine
DUNS #
City
Cincinnati
State
OH
Country
United States
Zip Code
45221
Zhu, L; Marvin, M J; Gardiner, A et al. (1999) Cerberus regulates left-right asymmetry of the embryonic head and heart. Curr Biol 9:931-8
Katsube, Y; Yokoshiki, H; Nguyen, L et al. (1998) Inhibition of Ca2+ current in neonatal and adult rat ventricular myocytes by the tyrosine kinase inhibitor, genistein. Eur J Pharmacol 345:309-14
Sumii, K; Imazu, M; Yamakido, M et al. (1997) Cyclic GMP-dependent protein kinase regulates the L-type calcium current in rat ventricular myocytes. Heart Vessels Suppl 12:62-5
Katsube, Y; Sperelakis, N (1996) Na+/Ca2+ exchange current: lack of effect of taurine. Eur J Pharmacol 316:97-103
Masuda, H; Sumii, K; Sperelakis, N (1996) Developmental changes in beta-adrenergic and muscarinic modulations of Ca2+ currents in fetal and neonatal ventricular cardiomyocytes of the rat. Reprod Fertil Dev 8:129-35
Yokoshiki, H; Sumii, K; Sperelakis, N (1996) Inhibition of L-type calcium current in rat ventricular cells by the tyrosine kinase inhibitor, genistein and its inactive analog, daidzein. J Mol Cell Cardiol 28:807-14
Masuda, H; Sumii, K; Sperelakis, N (1995) Long openings of calcium channels in fetal rat ventricular cardiomyocytes. Pflugers Arch 429:595-7
Conforti, L; Sumii, K; Sperelakis, N (1995) Dioctanoyl-glycerol inhibits L-type calcium current in embryonic chick cardiomyocytes independent of protein kinase C activation. J Mol Cell Cardiol 27:1219-24
Sumii, K; Sperelakis, N (1995) cGMP-dependent protein kinase regulation of the L-type Ca2+ current in rat ventricular myocytes. Circ Res 77:803-12
Haddad, G E; Sperelakis, N; Bkaily, G (1995) Regulation of the calcium slow channel by cyclic GMP dependent protein kinase in chick heart cells. Mol Cell Biochem 148:89-94

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