Isolated congenital asplenia: An overlooked cause of thrombocytosis

1. The local dilative effect of the calcium entry blocker nifedipine on forearm arteries and dorsal hand veins has been studied in 27 healthy male volunteers. 2. Nifedipine induced an increase of blood flow by 1190% (P less than 0.001) in the forearm. 3. The construction of the hand veins induced by stimulation of either postsynaptic alpha 1- or alpha 2-adrenoceptors was reduced (P less than 0.001) by nifedipine. 4. The calcium entry blocker nifedipine is a potent dilator of human forearm arteries as well as of dorsal hand veins.