Papaverine and Ro 20-1724 inhibit cyclic nucleotide phosphodiesterase activity and increase cyclic AMP levels in psoriatic epidermis in vitro

Abstract

The comparative inhibitory potency of papaverine and Ro 20-1724 (4-(3-butoxy-4-methoxybenzyl)-2-inidazolidinone) on cyclic AMP-phosphodiesterase (cAMP-PDE) and cyclic GMP-phosphodiesterase (cGMP-PDE) activities and their effect on the levels of cAMP and cGMP were examined in psoriatic epidermis. At concentrations of 5 x 10-4 M, papaverine inhibited the hydrolysis of both cAMP and cGMP by either the low or high Km psoriatic epidermal PDE nearly 100% (p < .0001) but had no significant effect on cGMP hydrolysis. When keratomed psoriatic epidermal slices were incubated in 5 x 10-4 M papaverine or Ro 20-1724 the tissue levels of cAMP were increase 343% or 1395% respectively (p