LY83583 is an inhibitor of soluble guanylate cyclase and of cGMP production [1].

Soluble Guanylate cyclase (sGC) is a heterodimeric enzyme involved in converting guanosine triphosphate to cyclic guanosine monophosphate. Soluble Guanylate cyclase is a critical component of the NO/cGMP signaling pathway, which has been involved in a number of important physiological processes, including smooth muscle relaxation and neurotransmission [2].

In human platelets, LY 83583 significantly antagonized the inhibitory effect of sodium nitroprusside and EDRF. LY 83583 attenuated the increases in intracellular cyclic GMP by sodium nitroprusside and EDRF [1]. Low concentrations of LY 83583 (≤ 0.1 μM) inhibited endothelium-dependent relaxations of rabbit aortic strips induced by acetylcholine or by the calcium ionophore A23187. Higher concentrations (≥ 0.3 μM) produced partial inhibition of relaxation to sodium nitroprusside and glyceryl trinitrate. LY 83583 (10 μM) showed no effect on cyclic AMP-mediated relaxations induced by isoprenaline or forskolin [3]. In cultured endothelial cells, treatment with LY 83583 (1 μM) rapidly and reversibly inhibited EDRF release. In the rat gastric fundus, LY 83583 (10 μM) inhibited the relaxation induced by nitric oxide (NO) [4]. In activated human neutrophils, LY-83583 (100 μM) inhibited the release of both LF and MPO after stimulation with FMLP or A-23187. LY-83583 reduced the cGMP-dependent protein kinase (G-kinase) activity [5].

References:
[1] Mülsch A, Lückhoff A, Pohl U, et al.  LY 83583 (6-anilino-5, 8-quinolinedione) blocks nitrovasodilator-induced cyclic GMP increases and inhibition of platelet activation[J]. Naunyn-Schmiedeberg's archives of pharmacology, 1989, 340(1): 119-125.
[2] Denninger J W, Marletta M A.  Guanylate cyclase and the NO/cGMP signaling pathway[J]. Biochimica et Biophysica Acta (BBA)-Bioenergetics, 1999, 1411(2): 334-350.
[3] Mülsch A, Busse R, Liebau S, et al.  LY 83583 interferes with the release of endothelium-derived relaxing factor and inhibits soluble guanylate cyclase[J]. Journal of Pharmacology and Experimental Therapeutics, 1988, 247(1): 283-288.
[4] Barbier A J M, Lefebvre R A.  Effect of LY 83583 on relaxation induced by non-adrenergic non-cholinergic nerve stimulation and exogenous nitric oxide in the rat gastric fundus[J]. European journal of pharmacology, 1992, 219(2): 331-334.
[5] Wyatt T A, Lincoln T M, Pryzwansky K B.  Regulation of human neutrophil degranulation by LY-83583 and L-arginine: role of cGMP-dependent protein kinase[J]. American Journal of Physiology-Cell Physiology, 1993, 265(1): C201-C211.