Elimination of smooth muscle cells in experimental restenosis: targeting of fibroblast growth factor receptors.

Factors in plasma and platelets do not fully account for the proliferation of smooth muscle cells in vascular injury, implying that additional factors are involved. Recently, we and others have observed that vascular injury regulates basic fibroblast growth factor, suggesting a further role for this pleiotropic factor. We report here that injury of rat arteries leads to an increase in fibroblast growth factor receptors in vascular smooth muscle cells. This up-regulation makes smooth muscle cells susceptible, in vitro and in vivo, to the lethal effects of a conjugate of basic fibroblast growth factor with the ribosome inactivator saporin. Saporin alone has no effect, whereas the conjugate kills proliferating, but not quiescent, smooth muscle cells in vitro. In vivo, one to three doses inhibit neointimal proliferation but have no apparent effect on the uninjured artery. Thus, the up-regulation of fibroblast growth factor receptors in vascular injury suggests new therapeutic possibilities for such refractory conditions as restenosis following balloon angioplasty.

Transforming growth factor beta-1 in acute myocardial infarction in rats.

TGF-beta 1 has been examined in the heart during myocardial infarction caused by ligation of the left coronary artery. Infarcted and uninfarcted myocardium have been compared by immunohistochemical staining of TGF-beta 1 and by Northern blot analysis of mRNA. Normal ventricular myocytes are strongly stained by an antibody to TGF-beta 1. Progressive loss of staining of these myocytes begins within 1 hr after coronary ligation. However, by 24-48 hr after ligation, intense staining of myocytes at the margin of infarcted areas is seen. Northern blots of infarcted myocardium 48 hr after ligation show a 3- to 4-fold increase in the principal 2.4 kb TGF-beta 1 mRNA; there is also a marked increase in a minor 1.9 kb transcript. In the same tissue samples, there is a 2-fold decrease in the mRNA for the glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase. The results indicate a significant role for TGF-beta in the response of the heart to injury.

Correlation of changes in cardiac calcium channels with hemodynamics in Syrian hamster cardiomyopathy and heart failure.

We compared hemodynamics with [3H]nitrendipine (calcium channel) binding to cardiac membranes from Bio 14.6 cardiomyopathic Syrian hamsters at 4 and 10 months with their F1B controls. A 50% increase in the number (Bmax) of nitrendipine binding sites (calcium channels) was seen only in the 4 month old myopathic vs controls (Bmax = 468 +/- 11 vs 309 +/- 10 fmol/mg prot with no change in affinity (KD) (KD = .65 +/- .12 vs .75 +/- .14 nM), while no differences in Bmax or KD were seen at 10 months (Bmax = 375 +/- 9 vs 362 +/- 7 fmol/mg prot/KD = .82 +/- .18 vs .89 +/- .17 nM) myopathic vs control respectively. Hemodynamic studies revealed no significant differences in cardiac output, cardiac index, stroke volume, heart rate, mean arterial pressure, peripheral resistance, body weight, heart weight at 4 months, but a significant decrease in peripheral resistance (1120 +/- 360 vs 2080 +/- 240) increase in body weight (118 +/- 2 vs 94 +/- 2 grams) and heart weight (97 +/- 5 vs 78 +/- 2 gms/100 gms body weight) in 10 month myopathic vs control animals. We conclude that the onset of cardiomyopathy at 4 months is associated with a selective increase in calcium channel binding sites and heart failure at 10 months is associated with a relative decrease in these sites.

A new device for the efficient pulverisation and extraction of myocardial biopsies for high energy phosphate analysis.

We developed a new device for processing frozen myocardial biopsies. Frozen samples of 20 to 50 mg were dropped into a 25 ml stainless steel centrifuge tube held in a custom-made aluminium container precooled in liquid nitrogen. A stainless steel pestle attached to a stainless steel disk was driven by a modified heavy-duty staple gun to pulverise the tissue rapidly at low temperatures. The tissue powder was extracted with 0.3N PCA at 0 degree C in the centrifuge tube which was then transferred to a Sorvall super-speed centrifuge. Values for adenosine triphosphate (ATP) were 5.6 +/- 0.7 mumol . g-1 wet weight (mean +/- SD). Creatine phosphate (CP) yield was 12.2 +/- 3 mumol . g-1 wet weight. The % recovery of an added internal standard for ATP was 86 +/- 18% and for CP 90 +/- 16% with the new method.

Comparative effects of verapamil, diltiazem, and nifedipine on hemodynamics and left ventricular function during acute myocardial ischemia in dogs.

The calcium channel-blocking drugs verapamil, diltiazem, and nifedipine are being used with increasing frequency in patients with angina pectoris due to coronary artery disease. Although each of these agents possesses negative inotropic potential, their relative effects on myocardial function in relation to their vasodilator potencies are unknown. We understood to study this in 20 conscious dogs that had partial occlusions of their circumflex coronary arteries during therapy with placebo, verapamil, nifedipine, or diltiazem. Myocardial blood flow was measured by use of microspheres, and left ventricular function was measured by radionuclide angiography. Drug effects were compared at doses causing equal decreases in mean arterial pressure and coronary vascular resistance of nonischemic myocardium. Global ejection fraction and ejection fraction of the ischemic region were significantly decreased by verapamil (p less than .01) and increased by nifedipine (p less than .001); diltiazem caused no significant changes. Verapamil significantly increased peak diastolic filling rate (p less than .001); nifedipine also increased diastolic filling rate, but only at doses that markedly decreased mean arterial pressure and coronary vascular resistance. The effect of diltiazem on diastolic filling rate was not significantly different than placebo. For doses causing an equal decrease in mean arterial pressure, verapamil decreased heart rate (p less than .001), and diltiazem and nifedipine increased heart rate (p less than .001). We conclude that the relative potencies of these three calcium channel blocking agents on left ventricular systolic and diastolic function during myocardial ischemia are different when compared with their relative vasodilator potencies. These differences may have important clinical implications.