H. Wahlander et al., MYOCARDIAL CAPILLARY DIFFUSION CAPACITY IN RAT HEARTS WITH CARDIAC-HYPERTROPHY DUE TO PRESSURE AND VOLUME OVERLOAD, The American journal of physiology, 265(1), 1993, pp. 80000061-80000068
The functional adaptation of the myocardial capillary bed in response
to cardiac hypertrophy was studied in one volume overload (aortocaval
fistula, ACF) and in one pressure overload model [left renal arterial
stenosis, two-kidney, one-clip (2K,1C)]. Furthermore, a group where re
nal hypertention was reversed 1 wk before experimentation (UC-2K,1C) a
nd a sham-operated (Sham) group were studied. Functional estimations o
f myocardial capillary diffusion capacity in terms of permeability sur
face area products (PS) per 100 g of myocardium were obtained by the s
ingle-injection indicator dilution technique in a Langendorff preparat
ion. After 4 wk, ACF hearts, with 72% hypertrophy and normal minimal c
oronary vascular resistance (CVR), displayed an unchanged diffusion ca
pacity, i.e., PS for Cr-EDTA and vitamin B-12. This indicates a struct
ural outgrowth of the coronary vascular bed to match the increased dem
and of the tissue. 2K,1C hearts with marked elevations of minimal coro
nary vascular resistance and left ventricular hypertrophy (65%) showed
higher PS values than Sham, implying that diffusion capacity was enha
nced despite structural coronary vascular changes. These changes were
completely reversed in UC-2K,1C. Thus the present data imply that myoc
ardial capillary diffusion capacity was well maintained in volume over
loaded cardiac hypertrophy and in contrast with earlier morphometric e
stimations, even enhanced in pressure overload hypertrophy.