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1. Effects of drugs acting on adrenergic and adenosine receptors on the intraocular pressure and the activity of adenylyl cyclase in ciliary processes and their sensitivity to pertussis toxin

Creator:
Čepelík, J., Caicedo, M., Dědina, M., and Hynie, S.
Type:
article, model:article, and TEXT
Subject:
adenosine agonists, adenylyl cyclase, adrenergic agonists, intraocular pressure, and pertussis toxin
Language:
English
Description:
The effects of the selective alpha2-adrenergic agonist p-aminoclonidine, the nonselective adrenergic agonist epinephrine, the selective beta2-adrenergic agonist fenoterol and the adenosine Ai agonist R-PLA on intraocular pressure were studied in control and pertussis toxin-pretreated rabbits. Pretreatment of rabbits with pertussis toxin decreased the ocular hypotensive effects of p-aminoclonidine and epinephrine, did not influence the same effects of fenoterol or R-PIA and markedly potentiated the initial ocular hypertensive effects of epinephrine and R-PIA. As far as the action on adenylyl cyclase in ciliary processes is concerned, isoproterenol stimulated its activity in control rabbits and epinephrine exerted dual, i.e. stimulatory and inhibitory effects on the activity of this enzyme. The data obtained with epinephrine and p-aminoclonidine confirm the view that their ocular hypotensive effects are associated with their inhibitory action on adenylyl cyclase and contradict the opinion that the hypotensive action of adrenergic drugs depends on adenylyl cyclase activation.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2. Effects of pertussis toxin treatment of rats on estradiol-induced adenohypophyseal growth reaction and on adrenergic lipolysis

Creator:
Hynie, S. and Klenerová, V.
Type:
article, model:article, and TEXT
Subject:
adenohypophysis, adenylyl cyclase, estradiol, forskolin, isoprénaline, lipolysis, pertussis toxin, and rat
Language:
English
Description:
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.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. The effects of adrenergic agonists on intraocular pressure and on adenylyl cyclase activity of ciliary processes in pigmented rabbits

Creator:
Čepelík, J., Dědina, M., and Hynie, S.
Type:
article, model:article, and TEXT
Subject:
adenylyl cyclase, adrenergic agonists, ciliary processes, desensitization, and intraocular pressure
Language:
English
Description:
The effects of /¿-adrenergic agonists isoprenaline, fenoterol and clenbuterol on the activity of adenylyl cyclase from ciliary processes and on intraocular pressure were examined in pigmented rabbits. Isoprenaline, fenoterol and clenbuterol stimulated adenylyl cyclase activity in vitro, but clenbuterol behaved as a partial agonist. Preincubation of ciliary processes with any of these three drugs led to the heterologous desensitization of adenylyl cyclase to the stimulatory effects of beta-adrenergic agonists or vasoactive intestinal peptide (VIP). This desensitization was dose-dependent and was expressed mainly as a decrease of the highest effects of stimulatory drugs. The exact mechanism of this phenomenon is not yet known. After topical administration, all three tested /¿-adrenergic agonists decreased intraocular pressure with approximately the same intensity. The relationship between ocular hypotensive effects of /¿-adrenergic agonists and their effects on adenylyl cyclase of ciliary processes is discussed. It is concluded that ocular hypotensive effects of adrenergic agonists and other drugs stimulating adenylyl cyclase cannot be explained simply by stimulation or desensitization of adenylyl cyclase of ciliary processes.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public