Effects of cobalt or nickel on the sympathetically mediated contractile responses in rat-isolated vas deferens.
Subchronic (30 days) exposure of rats to Co(NO3)2 or NiSO4 (20 mg.kg-1) in drinking water caused suppression of the isolated vas deferens contractile responses to exogenous adenosine 5'-triphosphate (ATP), noradrenaline, and l-phenylephrine, shifting the concentration-response curves to the relevant agonist to the right. Both metals facilitated the alpha 1-adrenoceptor antagonistic effects of prazosin, which resulted in increased pA2 values for the drug (9.68 +/- 0.13 in controls vs. 10.15 +/- 0.12 in Co(2+)-treated preparations and 12.60 +/- 0.67 in Ni(2+)-treated preparations). The inhibitory effect of clonidine on the contractions in response to low-frequency electrical field stimulation (EFS) in metal-treated preparations was decreased with pD2 values: 10.52 +/- 0.04 in controls, 9.56 +/- 0.13 in Co(2+)-treated preparations and 9.92 +/- 0.16 in Ni(2+)-treated preparations. The monophasic contractile responses to low-frequency EFS (0.1 Hz, 1 ms, 80 V) as well as the first phase of the biphasic contractions after high-frequency long-lasting EFS (300 pulses, 0.1 ms, 40 V, at 4, 8 or 20 Hz) were significantly increased in both groups of heavy metal-treated preparations. Therefore, subchronic exposure to Co2+ or Ni2+ leads to changes in pre- and postjunctional mechanisms underlying the sympathetically mediated contractile activity of isolated rat vas deferens.
Mutafova-Yambolieva
V
V
Department of Experimental Pharmacology, Bulgarian Academy of Sciences, Sofia.
Staneva-Stoytcheva
D
D
Lasova
L
L
Radomirov
R
R
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D003035:Cobalt / Q000008:administration & dosage*; D004558:Electric Stimulation; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009532:Nickel / Q000008:administration & dosage*; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011983:Receptors, Purinergic / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*; D014649:Vas Deferens / Q000187:drug effects / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
D011941:Receptors, Adrenergic; D011983:Receptors, Purinergic; D010656:Phenylephrine; D015016:Yohimbine; D003035:Cobalt; D009532:Nickel; D000255:Adenosine Triphosphate; D009638:Norepinephrine