FORCE PRODUCTION IN MECHANICALLY ISOLATED CARDIAC MYOCYTES FROM HUMANVENTRICULAR MUSCLE-TISSUE

Objective: The expression of contractile isoforms changes during vario us pathological conditions but little is known about the consequences of these changes for the mechanical properties in human ventricular mu scle. We investigated the feasibility of simultaneous determination of protein composition and isometric force development in single cardiac myocytes fr om human ventricular muscle tissue obtained from small bi opsies taken during open heart surgery. Methods: Small biopsies of abo ut 3 mg wet weight were taken during open heart surgery from patients with aortic valve stenosis. These biopsies were divided in two parts. One part(similar to 2 mg) was used for mechanical isolation of single myocytes and subsequent force measurement while the remaining part was used, in aliquots of 1 mu g dry weight, for protein analysis by polya crylamide gel electrophoresis. The myocytes were attached with silicon glue to a sensitive force transducer and a piezoelectric motor, mount ed on an inverted microscope and permeabilized by means of Triton X-10 0. Force development was studied at various free calcium concentration s. Results: From all biopsies, myocytes could be obtained and the comp osition of contractile proteins could be determined. The average isome tric force (+/-s.e.m.) at saturating calcium concentration obtained on 20 myocytes from 5 patients amounted to 51 +/- 8 kN/m(2). Force was h alf maximal at a calcium concentration of 2.47 +/- 0.10 IJ hl. Conclus ion: These measurements indicate that it is possible to study the corr elation between mechanical properties and protein composition in small biopsies from human ventricular muscle. (C) 1998 Elsevier Science B.V . All rights reserved.