The effect of calcium antagonism on myocardial relaxation

THF FFFRCT OF CIALCIrJP4 AMTAr,CWISEI 0x1 MYOCIAR~IAL ?.FLAXATIOM. Cingolani,H.F.,(7elpi,R.J.,Mosca,S~.,Rinaldi G.J.,Kosoqlov A. Centro de Investigaciones Cardiovas xares. LA PJ,ATA (19GO), ARGFWI~~A. In open-chest anesthetized doqs Prenylamine (P), Verapamil (V) and Mifedipine (h?) were injected in a dose necesarv to decrease the tension d.eveloned hv an isometric left ventricular segment hv anproximately 30%. The time course of their effect on arterial pressure (AP),heart rate (W), maxi?al rate of LV pressure development (+?) and fall (;P), and maximal rate of LV tension development (+v) and fall (-?) was studied. A0 was significantly decreased hv an averaqe of 4U mmHq, while HR showed not silqnificant variations: A nroportionallv qreater decrease in -6 than in +P was observed (Pe.05). ?hzs yas reflected hv signifilant increases $n the +P/-P ratio? (increments of.34 -.13 for Pi.31 -.08 for V.anc.32 12 for N). Siqnificant increments in the +T/-v rakos were also'found sugqestina that the proportionallv qreater decrease in relaxation was not a result of altered loadinq to the heart.When contractilitv was depressed in a similar extent hv administration of d-l propranolol and sodivm ncntobarhital proportional equal decrease? in +P, -P, +?', -T, were record ed.The +6/-P and +?'/-" ratios remain now unaltered.It is concluded that calcium antaaonists have a selective action on relaxation.

CARBON MONOXIDE INDUCED CARDIOMEGALY IN NEONATAL RATS. Fred J. Clubb, Jr., S. P. Bishop, Dept. of Pathology, UAB, Birmingham, AL 35294; D.G. Penney and M.S. Baylerian, Dept. of Physiology, Wayne State Univ., Detroit, MI 48201 Newborn Sprague-Dawley rats were either raised in room air (A) or exposed to carbon monoxide (CO, 200ppm) from birth to 28 days age to determine if added stress would affect the transition of myocardial cells from hyperplastic to hypertrophic At specific time periods (birth,4,6,9,12,15,21, and growth. were studied: body weight(BW); total 28d1, the following heart weight (BW); left ventricle plus septum (LV+S) and right ventricle (RV) wet and dry weights; and percent binucleation (2N) and cell volume (CV), using a Coulter cell size s&em, from isolated myocytes obtained by perfusion with Ca free Joklik media containing 0.1% collagenase. Dry weights in both groups increased from 16.5+0.8% (SEMI at birth to 21.2?0.2% at 28d. CO BW/BW was increased from 9-28d (p
29