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1. This study investigated the possibility that adenosine receptors modulate the alpha(1)-adrenoceptor-mediated contractility of human cultured prostatic stromal cells (HCPSC). 2. The nonselective adenosine receptor agonist, 5'-N-ethylcarboxamido-adenosine (NECA; 10 nm-10 microm), and the A(1) adenosine receptor selective agonist, cyclopentyladenosine (CPA; 10 nm-10 microm), elicited significant contractions in HCPSC, with maximum contractile responses of 18+/-3% and 17+/-2% reduction in initial cell length, respectively. 3. In the presence of a threshold concentration of phenylephrine (PE) (100 nm), CPA (1 nm-10 microm) caused contractions, with an EC(50) of 124+/-12 nm and maximum contractile response of 37+/-4%. The A(1) adenosine receptor-selective antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX 100 nm) blocked this effect. In the presence of DPCPX (100 nm), NECA (1 nm-10 microm) inhibited contractions elicited by a submaximal concentration of PE (10 microm), with an IC(50) of 48+/-2 nm. The A(2A) adenosine receptor-selective antagonist 4-(2-[7-amino-2-[furyl][1,2,4]triazolo[2,3-alpha][1,3,5,]triazin-5-yl amino]ethyl)phenol (Zm241385 100 nm) blocked this effect. 4. In BCECF-AM (10 microm)-loaded cells, both CPA (100 pM-1 microm) and NECA (100 pm-10 microm) elicited concentration-dependent decreases in intracellular pH (pH(i)), with EC(50) values of 3.1+/-0.3 and 6.0+/-0.3 nm, respectively. The response to NECA was blocked by Zm241385 (100 nm; apparent pK(B) of 9.4+/-0.4), but not by DPCPX (100 nm). The maximum response to CPA was blocked by DPCPX (100 nm), and unaffected by Zm241385 (100 nm). 5. NECA (10 nm-10 microm) alone did not increase [(3)H]-cAMP in HCPSC. In the presence of DPCPX (100 nm), NECA (10 nm-10 microm) caused a concentration dependent increase in [(3)H]-cAMP, with an EC(50) of 1.2+/-0.1 microm. This response was inhibited by Zm241385 (100 nm). CPA (10 nm-10 microm) had no effect on cAMP, in the presence or absence of forskolin (1 microm). 6. These findings are consistent with a role for adenosine receptors in the modulation of adrenoceptor-mediated contractility in human prostate-derived cells.

1 We have investigated the effects of alpha(1)-adrenoceptor stimulation upon contractility, Ca(2+) influx, inositol phosphate production, and protein kinase C (PKC) translocation in human cultured prostatic stromal cells (HCPSC). 2 The alpha(1)-adrenoceptor selective agonist phenylephrine elicited contractile responses of HCPSC, i.e. a maximal cell shortening of 45+/-6% of initial cell length, with an EC(50) of 1.6+/-0.1 microM. The alpha(1)-adrenoceptor selective antagonists prazosin (1 microM) and terazosin (1 microM) both blocked contractions to phenylephrine (10 microM). The L-type calcium channel blocker nifedipine (10 microM), and the PKC inhibitors Gö 6976 (1 microM) and bisindolylmaleimide (1 microM) also inhibited phenylephrine-induced contractions. 3 Phenylephrine caused a concentration dependent increase in inositol phosphate production (EC(50) 119+/-67 nM). This response was blocked by terazosin (1 microM). 4 Phenylephrine caused the translocation of the PKC alpha isoform, but not the beta, delta, gamma, epsilon or lambda isoforms, from the cytosolic to the particulate fraction of HCPSC, with an EC(50) of 5.7+/-0.5 microM. 5 In FURA-2AM (5 microM) loaded cells, phenylephrine elicited concentration dependent increases in [Ca(2+)](i), with an EC(50) of 3.9+/-0.4 microM. The response to phenylephrine (10 microM) was blocked by prazosin (1 microM), bisindolymaleimide (1 microM), and nifedipine (10 microM). 6 In conclusion, this study has shown that HCPSC express functional alpha(1)-adrenoceptors, and that the intracellular pathways responsible for contractility may be largely dependent upon protein kinase C activation and subsequent opening of L-type calcium channels.