Electrophoretic separation and quantitation of cardiac myosin heavy chain isoforms in eight mammalian species

A protocol for sample preparation and gel electrophoresis is described that reliably results in the separation of the alpha- and beta-isoforms of cardiac myosin heavy chain (MHC-alpha and MHC-beta) in eight mammalian species. The protocol is based on a simple, nongradient denaturing gel. The magnitude of separation of MHC-alpha and MHC-beta achieved with this protocol is sufficient for quantitative determination of the relative amounts of these two isoforms in mouse, rat, guinea pig, rabbit, canine, pig, baboon, and human myocardial samples. The sensitivity of the protocol is sufficient for the detection of MHC isoforms in samples at least as small as 1 mu g. The glycerol concentration in the separating gel is an important factor for successfully separating MHC-alpha and MHC-beta in myocardial samples from different species. The effect of sample load on MHC-alpha and MHC-beta band resolution is illustrated. The results also indicate that inclusion of a homogenization step during sample preparation increases the amount of MHC detected on the gel for cardiac samples to a much greater extent than for skeletal muscle samples. Although the protocol described in this study is excellent for analyzing cardiac samples, it should be noted that the same protocol is not optimal for separating MHC isoforms expressed in skeletal muscle, as is illustrated.