The method of cellular immobilization and perfusion was applied to adipocytes. The lipolytic effect of isoprénaline, whose action is produced as a result of receptor-drug interaction, was followed. An agarose solution kept at at 37 °C was mixed 1:1 with the cell suspension. Thereafter, adipocytes were immobilized in the agarose threads. The lipolytic effect of 0.1 ml of isoprénaline (1x10~4 mol/1), that was rapidly introduced to the cell perfusion inlet in a non-recirculating system, was monitored by assessing glycerol production. The immobilized and perfused adipocytes exhibited significant lipolytic activity. After reaching the maximum effect, 0.1 ml of propranol (lxl 0-3 mol/1) that was applied to the bioreactor inlet, abolished the isoprénaline effect. The present data demonstrate the potential applicability of immobilized perfused adipocytes for various kinds of studies.
After long-lasting administration of estradiol (4—6 weeks) in the presence or absence of pertussis toxin treatment we followed up the changes in body weight and adenohypophyseal weight in rats subjected to this treatment. The most striking effect was the potentiating effect of pertussis toxin on the estradiol-induced adenohypophyseal growth reaction. Adenylyl cyclase activity in the adenohypophysis was significantly increased in the estradiol- treated group and the addition of pertussis toxin did not further increase this enzyme activity. The lipolytic activity in adipose tissue exhibited a similar response as adenohypophyseal growth. Adrenergic lipolysis stimulated by pertussis toxin was highly significantly increased in tissues of rats treated with pertussis toxin. Our results show that the estrogen-induced adenohypophyseal growth reaction is highly potentiated by the treatment of rats with pertussis toxin and that this effect is in many aspects similar to that observed in adrenergic lipolysis. It thus seems that both processes might be mediated via a pertussis toxin-sensitive G protein which is involved in inhibitory regulation of adenylyl cyclase.
We investigated the effect of isoprénaline (IPRO), a /J-mimetic catecholamine, on incorporation of (32P)Pi into phospholipids of the mouse left ventricle in uiuo. All experimental groups of male mice received an injection of (32p)pi ^250 MBq x kg“1 b.w.) intraperitoneally two hours prior to sacrifice. A single dose of IPRO (5 mg x kg-1 b.w.) was injected one hour before killing. IPRO increased the specific radioactivity of phosphatidylcholine (PC) by a factor of 1.8, diphosphatidylglycerol (DPG) 2.1, sphingomyelin (SM) 3.5, phosphatidylinositol (PI) 1.7, phosphatidylserine (PS) 1.7, phosphatidylglycerol (PG) 1.7, phosphatidic acid (PA) 2.0 compared to control values. On the other hand, IPRO is also known to stimulate phospholipid degradation by activation of phospholipase A2. That is why we used mepacrine (50 mg x kg“1 b.w.), a phospholipase inhibitor, to find a possible link between biosynthesis and degradation of phospholipids. Pretreatment with mepacrine two hours prior to sacrifice suppressed IPRO stimulated incorporation of (32P)Pi into phospholipids nearly to control levels. Mepacrine itself did not significantly influence the specific radioactivity of phospholipids. We conclude that phospholipase A2 inhibitor, mepacrine, is able to prevent IPRO-stimulated ¡corporation into phospholipids, suggesting a feedback relation between their biosynthesis and degradation in the myocardium.