Complex sentence: Another, vasicinone, showed bronchodilatory activity "in vitro" but bronchoconstrictory activity "in vivo"; it is probably biotransformed "in vivo", causing bronchoconstriction.
Split into simpler sentences: Another, vasicinone, showed bronchodilatory activity "in vitro" but bronchoconstrictory activity "in vivo". It is probably biotransformed "in vivo", causing bronchoconstriction.