title: Dipyridamole-induced capillary growth in normal and hypertrophic hearts.
abstract: Chronic increases in myocardial blood flow have been shown to stimulate capillary proliferation in normal growing hearts. It is unknown, however, if elevated myocardial blood flow stimulates precapillary and/or capillary growth in hearts undergoing hypertrophy. Accordingly, renal hypertension was produced in rabbits (Page, 1-kidney, 1-wrap model) in which one group of Page (n = 9) and one group of normotensive sham (n = 10) rabbits were given dipyridamole (4.0 mg/kg sc) twice daily for 2 mo. Another group of Page (n = 7) and sham (n = 12) rabbits received vehicle injections. In separate acute studies performed on conscious rabbits, this does of dipyridamole increased myocardial blood flow 35-60% over time without altering transmural distribution of flow or systemic blood pressure. Two months later, minimal coronary vascular resistance (MCVR/100 g) was calculated from perfusion during maximal coronary vasodilation in conscious animals. Histomorphometric methods were then utilized to evaluate various indexes of capillarity in perfuse-fixed hearts. Systolic pressure and left ventricle weight-to-body weight ratios were significantly higher in Page vs. sham rabbits; dipyridamole treatment did not alter these parameters within either group. Similarly, dipyridamole treatment did not significantly alter MCVR/100 g values in either normotensive or hypertensive rabbits. In contrast, dipyridamole treatment increased endomyocardial capillary length density by 33% in the hypertensive group (P less than 0.05) and 11% in the sham group (P not significant) compared with the respective vehicle-treated rabbits. In addition, intercapillary distance was significantly reduced in the endomyocardial region of both groups receiving dipyridamole injections.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Anatomy, University of Iowa, Iowa City 52242.
authors.forename: R J
authors.initials: RJ
authors.lastname: Torry
authors.forename: D M
authors.initials: DM
authors.lastname: O'Brien
authors.forename: P M
authors.initials: PM
authors.lastname: Connell
authors.forename: R J
authors.initials: RJ
authors.lastname: Tomanek
mesh_terms: D000818:Animals; D002196:Capillaries / Q000254:growth & development; D006332:Cardiomegaly / Q000503:physiopathology*; D003326:Coronary Circulation / Q000187:drug effects*; D004176:Dipyridamole / Q000494:pharmacology*; D006977:Hypertension, Renal / Q000503:physiopathology; D008297:Male; D009389:Neovascularization, Pathologic / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology; D011817:Rabbits; D012016:Reference Values; D013997:Time Factors
chemical_list: D004176:Dipyridamole