Specific features in the reactivity of visceral smooth muscle from spontaneously hypertensive rats
Petkov, O.; Venkova, K.
Acta Physiologica et Pharmacologica Bulgarica 8(4): 35-44
1982
ISSN/ISBN: 0323-9950 PMID: 7185263 Document Number: 195528
Experiments were carried out on male and female spontaneously hypertensive rats (SHR) belonging to 2 age groups: 2.5-4 mo. and 6-12 mo. Normotensive Wistar rats (NTR) of the same age and sex were used as controls. The experiments involved only SHR in which the ratio of myocardial weight per 100 g body wt exceeded very significantly the same ration in control NTR. Isolated longitudinal strip from the fundus of rat stomach was used as smooth-muscle preparation. Parallel experiments on smooth-muscle preparations from SHR and NTR gave the following results: NA (1 .times. 10-10 to 1 .times. 10-7 mol) manifests a tendency towards stronger contractile effects on SHR preparations. Indomethacin (3 .times. 10-5 mol) decreased more strongly the tone of SHR preparations, PGE2 (1 .times. 10-9 mol), applied on the background of indomethacin action, increased more strongly the tone of SHR preparations. The sex and age characteristics of the rats had no essential effect on the reactivity of the smooth-muscle preparation in most experiments. The results obtained suggest increased reactivity of the longitudinal stomach smooth muscle of SHR to NA. Taking into account the results previously obtained in other experiments (on rat vas deferens and anococcygeal muscle) and the data in the literature, an assumption is expressed concerning the mosaic character of the specific features of adrenergic transmission in SHR. The smooth-muscle preparations used manifest increased reactivity to 5-HT and ACh as well. Evidently, the specificities in the effects of indomethacine and PGE2 on SHR smooth-muscle preparations are possibly due to genetically conditioned damage of PGE2 synthesis in SHR.