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We have investigated the effects of α1‐adrenoceptor stimulation upon contractility, Ca2+ influx, inositol phosphate production, and protein kinase C (PKC) translocation in human cultured prostatic stromal cells (HCPSC). The α1‐adrenoceptor selective agonist phenylephrine elicited contractile responses of HCPSC, i.e. a maximal cell shortening of 45±6% of initial cell length, with an EC50 of 1.6±0.1 μM. The α1‐adrenoceptor selective antagonists prazosin (1 μM) and terazosin (1 μM) both blocked contractions to phenylephrine (10 μM). The L‐type calcium channel blocker nifedipine (10 μM), and the PKC inhibitors Gö 6976 (1 μM) and bisindolylmaleimide (1 μM) also inhibited phenylephrine‐induced contractions. Phenylephrine caused a concentration dependent increase in inositol phosphate production (EC50 119±67 nM). This response was blocked by terazosin (1 μM). Phenylephrine caused the translocation of the PKC α isoform, but not the β, δ, γ, ε or λ isoforms, from the cytosolic to the particulate fraction of HCPSC, with an EC50 of 5.7±0.5 μM. In FURA‐2AM (5 μM) loaded cells, phenylephrine elicited concentration dependent increases in [Ca2+]i, with an EC50 of 3.9±0.4 μM. The response to phenylephrine (10 μM) was blocked by prazosin (1 μM), bisindolymaleimide (1 μM), and nifedipine (10 μM). In conclusion, this study has shown that HCPSC express functional α1‐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. British Journal of Pharmacology (2003) 138, 218–224. doi:

This study investigated the possibility that adenosine receptors modulate the α1‐adrenoceptor‐mediated contractility of human cultured prostatic stromal cells (HCPSC). The nonselective adenosine receptor agonist, 5′‐N‐ethylcarboxamido‐adenosine (NECA; 10 nM–10 μM), and the A1 adenosine receptor selective agonist, cyclopentyladenosine (CPA; 10 nM–10 μM), elicited significant contractions in HCPSC, with maximum contractile responses of 18±3% and 17±2% reduction in initial cell length, respectively. In the presence of a threshold concentration of phenylephrine (PE) (100 nM), CPA (1 nM–10 μM) caused contractions, with an EC50 of 124±12 nM and maximum contractile response of 37±4%. The A1 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 μM) inhibited contractions elicited by a submaximal concentration of PE (10 μM), with an IC50 of 48±2 nM. The A2A adenosine receptor‐selective antagonist 4‐(2‐[7‐amino‐2‐{furyl}{1,2,4}triazolo{2,3‐α}{1,3,5,}triazin‐5‐yl amino]ethyl)phenol (Zm241385 100 nM) blocked this effect. In BCECF‐AM (10 μM)‐loaded cells, both CPA (100 pM–1 μM) and NECA (100 pM–10 μM) elicited concentration‐dependent decreases in intracellular pH (pHi), with EC50 values of 3.1±0.3 and 6.0±0.3 nM, respectively. The response to NECA was blocked by Zm241385 (100 nM; apparent pKB 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). NECA (10 nM–10 μM) alone did not increase [3H]‐cAMP in HCPSC. In the presence of DPCPX (100 nM), NECA (10 nM–10 μM) caused a concentration dependent increase in [3H]‐cAMP, with an EC50 of 1.2±0.1 μM. This response was inhibited by Zm241385 (100 nM). CPA (10 nM–10 μM) had no effect on cAMP, in the presence or absence of forskolin (1 μM). These findings are consistent with a role for adenosine receptors in the modulation of adrenoceptor‐mediated contractility in human prostate‐derived cells. British Journal of Pharmacology (2004) 141, 302–310. doi:

1 The aim of this study was to investigate the eects of adenine nucleosides and nucleotides on contractility of the smooth muscle of rat prostate gland. 2 Nerve terminals within rat isolated prostatic tissues were electrically ®eld stimulated (60 V, 0.5 ms, 10 Hz, 20 pulses every 60 s). Adenosine 5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP), adenosine 5'-monophosphate (AMP) and adenosine had no eect on baseline smooth muscle tone but concentration-dependently inhibited electrically-evoked contractile responses. The relative order of potency was ATP % AMP % adenosine4ADP. 3 The inhibition by ATP and adenosine of ®eld stimulation-induced contractions in the rat prostate was antagonized by 8-phenyltheophylline (10 mM), but not by suramin (100 mM) and only slightly by reactive blue 2 (5 mM). 4 The adenosine metabolizing enzyme adenosine deaminase (0.1 unit ml 71) inhibited the inhibitory eects of ATP and adenosine. The P2 purinoceptor agonist 2-methylthio ATP (10 nM ± 0.1 mM), had no eect on ®eld stimulation-induced contractions of the rat prostate. 5 ATP and adenosine did not modify the contractile responses of the rat prostate to exogenously added noradrenaline (10 mM). 6 Inhibitory concentration-response curves to a number of adenosine analogues with diering stabilities and selectivities for the dierent adenosine receptors yielded a relative rank order of agonist potency of:These results indicate that adenine nucleoside and nucleotide induced inhibition of electricallyevoked contractions in the rat prostate occurs through activation of adenosine but not ATP receptors. The relative order of potency of adenosine analogues is consistent with activation of receptors of the A 1 -adenosine receptor subtype. These receptors appear to be prejunctional.