Evidence for ryanodine receptors in Schistosoma mansoni.
The present study investigated the presence of ryanodine receptors in the trematode Schistosoma mansoni. [3H]Ryanodine specific binding sites were found in the four subcellular fractions of S. mansoni; however, more binding sites were recovered in the heterogeneous fraction P1 and the microsomal fraction P4, as was thapsigargin-sensitive (Ca2+-Mg2+)ATPase activity, marking the sarco/endoplasmic reticulum calcium ATPase (SERCA) pumps. This binding had an equilibrium dissociation constant (Kd) in the nanomolar range, an apparent maximal number of receptors (Bmax) of about 80 fmol/mg of protein, and was modulated by ions (Ca2+, Mg2+) and some pharmacological tools such as caffeine. Ryanodine was able to accelerate the rate of 45Ca2+ release from actively loaded vesicles, and also to induce a transient contraction of the whole worm. We conclude that ryanodine-sensitive Ca2+ release channels are present in S. mansoni, with properties very similar to the ones present in higher animals.
Departamento de Farmacologia Básica e Clínica, ICB, Universidade Federal do Rio de Janeiro, Cidade Universitária, RJ, Brazil.
C L
CL
Silva
V M
VM
Cunha
D L
DL
Mendonça-Silva
F
F
Noël
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D051381:Rats; D012433:Ryanodine / Q000494:pharmacology*; D019837:Ryanodine Receptor Calcium Release Channel / Q000032:analysis*; D012550:Schistosoma mansoni / Q000737:chemistry*
D015220:Calcium Channels; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D002118:Calcium