Abstract:1 In atrial preparations of the young guinea-pig (body weight 150-250 g), five proteolytic enzymes (trypsin, chymotrypsin, bacterial-Al-proteinase (nagarse), bromelain and kallikrein) produced concentration-dependent positive inotropic and chronotropic effects, while they exerted only minimal effects on the papillary muscle preparations. 2 To characterize the effects, further experiments were conducted in atrial preparations using trypsin. There was a strong tendency for tachyphylaxis: a second exposure to the… Show more
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