is used as the source of sgc an aliquot of the supernatant and the compound to be tested are added into a buffer containing gtp a substrate for sgc the activity of sgc can be determined by the method described in gerzer et al j pharmacol exp ther 1983 226 180 the efficacy of a compound in inhibiting pdes can be evaluated in vitro by the following assay washed platelets are suspended in a tris hcl buffer and disrupted by sonication the lysate is centrifuged to obtain a supernatant which contains pdes an aliquot of the supernatant is taken to prepare a pde containing solution the compound to be tested and cgmp a substrate for pde are added to the solution ophiophagus hannah snake venom is subsequently added to remove the phosphate in 5 u2032 gmp converted from cgmp by pdes to form uncharged guanosine an ion exchange resin is used to remove the remaining cgmp the cgmp free solution is then centrifuged and an aliquot of the supernatant is taken for quantification of the uncharged guanosine in a liquid scintillation counter activity of pdes is evaluated based on the amount of the uncharged guanosine in vitro assays can be used to evaluate the efficacy of a fused pyrazolyl compound of this invention in inhibiting platelet aggregation which is attributable to low intracellular cgmp levels for example the compound is incubated in a platelet suspension containing a platelet aggregation factor and the degree of aggregation is measured turbidimetrically with a dual channel lumiaggregometer and converted into a percentage value by the method described in teng et al biochem biophys acta 1987 924 375 382 in vivo screening can be performed by following procedures well known in the art without further elaboration it is believed that one skilled.