There is a substantial literature regarding cardiac hypertrophy in rats,
much of it over 20 years old.  In many forms of cardiac enlargement in
rats, the enlargement is accompanied by distinct polyploidization of the
myocytes.  Many of the reported studies measured myocyte ploidy as a
measure of extent of hypertrophy.  Since not all myocytes become
polyploid, the percentage of polyploid myocytes was used as a measure of
degree of hyeprtrophy.  The phenomenon was documented in various forms of
exercise induced cardiac hypertrophy, as well as in various forms of
drug-induced hypertrophy.

Cardiac myocyte polyploidization has also been documented in human heart
hypertrophy, but to my knowledge has never been used as a routine
diagnostic on cardiac biopsies.  That might make a fascinating study!

Al Floyd
23126 South Shore Drive
Edwardsburg, MI 49112
(269) 699-7182 phone & fax