Atrial natriuretic peptide (ANP), guanylate cyclase, and intraocular pressure in the rabbit eye

Abstract

Synthetic rat atrial natriuretic peptide (ANP) was examined for effects on guanylate-and on adenylate cyclase activity in ciliary process homogenates and for effects on intraocular pressure in the albino rabbit eye. Ciliary process guanylate cyclase was associated predominantly with the particulate fraction and was partially activated by ANP (EC50, approximately 1 nM) relative to a maximal dose of Na Nitroprusside (2 uM), whereas particulate adenylate cyclase (basal as well as forskolin-stimulated activity) showed no responses to ANP at doses up to 0.3 uM. Particulate cAMP phosphodiesterase activity was stimulated by low doses of cGMP (1-5 uM) in ciliary processes. Thus, ANP, acting via guanylate cyclase, has the potential to regulate phosphodiesterase activity and indirectly decrease cAMP levels in membranes derived from ciliary processes. Intravitreous injection of ANP (2-4 ug/eye) caused a small decrease (1-1.5 mm Hg) in intraocular pressure measured 16-24 hours after injection but the pressure had returned to normal by 40 hours. The findings demonstrate regulation of biochemical and pharmacological responses by ANP in the albino rabbit eye suggesting that this peptide may play a physiological role in secretory functions of ciliary processes.

Lack of circadian change of concentration of C-type natriuretic peptide in rabbit aqueous humor

“…Nevertheless, there is strong evidence that natriuretic peptides, especially CNP (2), can modulate intraocular pressure (2)(3)(4)(5)(13)(14)(15)(16) . Fernandez-Durango et al reported that the effect of CNP on intraocular pressure reduction was 9-fold and 20-fold higher than the effect of BNP and ANP, respectively (2) .…”

Moxonidine-lnduced Inhibition of Norepinephrine Release in Monkey and Rabbit Ciliary Bodies: Role of cGMP

“…Although cGMP activators, such as atrial natriuretic peptides and nitrovasodilators, can induce ocular hypotensive effects in rab bits [7,16], cGMP generation has not been implicated in the ocular action of cb-agonists. In the rabbit iris-ciliary body, there is an effect by moxonidine on cGMP production, confirming that there are several potential mechanisms of action for moxonidine.…”

“…Moreover, intravitreal administra tion of 8-Br-cGMP in monkeys decreased aqueous humor flow rates [6], Evidence sug gests that the suppressive effects of atrial na triuretic peptides on aqueous humor dynam ics in the rabbit are mediated, in part, by cGMP production in iris-ciliary body [7][8][9]. In other tissues and cells (vas deferens, vascu lar smooth muscle and PC 12 cells), cGMP suppresses catecholamine release [10][11][12], Thus, cGMP could also be an inhibitory modulator of norepinephrine release in sym pathetic nerves in the eye.…”

Naphazoline-Induced Neuroendocrine Changes: Increases in ANP and cGMP Levels, but Suppression of NE, ³H-NE, and cAMP Levels in Rabbit Eyes

“…The present study was designed to determine whether naphazoline could modulate atrial natriuretic peptide (ANP), norepinephrine (NE), and cyclic nucleotide (cAMP, cGMP) levels in fluids and/or tissues in rabbit eyes. Previous studies by a variety of investigators [1][2][3][4] suggested neuropeptide involvement in ocular hydrodynamics. More recently, an autocrine/paracrine (peptide-peptide receptor) loop in nonpigmented epithelial cells has been implicated in the regulation of aqueous humor dynamics [5].…”