Prenylamine inhibition of isoproterenol induced myocardial lesions. Histochemical and ultrastructural findings.

Eighty Wistar rats were divided into 4 groups. All of them received 10 mg/kg i.p. isoproterenol (ISP). The animals were sacrificed at 5 min. (groups A and B) and 24 hours (groups C and D). Groups A and C served as control of group B and D. Group B also received 9 mg/kg prenylamine (P), 30 min before ISP and group D 9 mg/kg P, 1 hour before and 1 hour after ISP. Transversal slices of each heart underwent the following procedures: hematoxilineosin, Barbeito-Lopez trichromic, "ischemia stain", acid phosphatase stain and standard electron microscopy. Group A and C showed positivity for ischemic techniques; necrotic and ischemic zones represented, in average 25.1 +/- 1.4% of the myocardial volume. Group B and D (ISP + prenylamine) showed no significant lesions. Group D (ISP + prenylamine, sacrificed at 24 hours) presented complete absence of "infarct-like" lesions in 17 out of the 20 studied animals. No evident changes in acid-phosphatase enzymes were detected. Animals treated with ISP alone presented "contraction bands" at electron microscopy as well as myofibrillar fragmentation. Those receiving also P showed only light alterations, in the electron microscopy specimens. A primary action of ISP on the calcium pump might explain the infarct-like lesions found in our study. The inhibition of these above mentioned lesions by prenylamine, a drug which acts by slowing down the ca transport, also supports this interpretation.