ABSTRACT
BACKGROUND/AIMS: Portal hypertension is associated with systemic vasodilatation and vascular hyporeactivity, and is reversed by inhibiting nitric oxide biosynthesis. Nitric oxide and calcitonin gene-related peptide are neurotransmitters of non-adrenergic non-cholinergic nerves. The role of nitric oxide and calcitonin gene-related peptide in nerve-stimulated vasodilatation in portal hypertension is unknown. METHODS: We tested (i) if in vitro perfused superior mesenteric arterial vascular beds of portal hypertensive rats (induced by partial portal vein ligation) showed an increased vasodilatation to periarterial nerve stimulation compared to normal controls, and (ii) if this vasodilatation was modulated by nitric oxide and calcitonin gene-related peptide antagonism. RESULTS: Vasodilatatory responses to periarterial nerve stimulation (10 V, 1 ms) with increasing frequencies (Hertz, 2-12) in preconstricted vessels (methoxamine and guanethidine) were significantly smaller in vessel preparations of control (n=8) compared to portal hypertensive (n=7) rats, values with 8 Hertz being 32.3+/-3.6% and 44.9+/-3.6%, respectively (p<0.05). This difference was reversed by inhibiting nitric oxide and calcitonin gene-related peptide action with the nitric oxide-biosynthesis inhibitor N(omega)-Nitro-L-arginine, values for 8 Hertz being 28.7+/-4.8% (controls) and 37.8+/-3.3% (portal hypertensive, ns) or with the calcitonin gene-related peptide antagonist CGRP8-37, values being 25.2+/-2.8% (controls) and 27.8+/-4.2% (portal hypertensive, ns), respectively (n=4-6 per group). Vasodilatation to the beta-agonist isoproterenol was not significantly different between groups with and without calcitonin gene-related peptide and nitric oxide antagonism. CONCLUSION: Portal hypertensive rats display a significantly enhanced vasodilatation to periarterial nerve stimulation, which is reversed by inhibiting the non-adrenergic non-cholinergic neurotransmitters nitric oxide and especially calcitonin gene-related peptide.
Subject(s)
Calcitonin Gene-Related Peptide/physiology , Hypertension, Portal/physiopathology , Mesenteric Artery, Superior/innervation , Mesenteric Artery, Superior/physiology , Muscle, Smooth, Vascular/innervation , Muscle, Smooth, Vascular/physiology , Nitric Oxide/physiology , Vasodilation/physiology , Animals , Calcitonin Gene-Related Peptide/pharmacology , Electric Stimulation , Male , Mesenteric Artery, Superior/physiopathology , Muscle, Smooth, Vascular/physiopathology , Nitroarginine/pharmacology , Peptide Fragments/pharmacology , Rats , Rats, Sprague-Dawley , Reference Values , Sympathetic Nervous System/physiology , Vasodilation/drug effectsABSTRACT
Portal hypertension goes along with vascular hyporeactivity, partly mediated by nitric oxide (NO). Interactions between the adrenergic nervous system and NO in portal hypertension are undetermined. We tested (1) whether superior mesenteric arterial beds of portal hypertensive rats have an altered sensitivity to periarterial nerve stimulation (PNS) and (2) the role of NO in modulating nerve-stimulated responses. Vasopressor responses to PNS (Hz, 2-32) were similar in preparations of partial portal vein-ligated (PVL, n = 12) and control (CON, n = 12) rats (60.0 +/- 6.7 and 47.8 +/- 6.1 CmH2O respectively) for 24 Hz (NS), but sensitivity of vessels of portal hypertensive animals displayed a significant rightward shift [Hz needed for 50% of maximal response (HZ50) being 15.5 +/- 0.4 and 12.9 +/- 0.6 for PVL and CON respectively, P < 0.001]. NO formation inhibition by N omega-nitro-L-arginine (10(-4) mol L-1) significantly increased responses to PNS (P < 0.05), the absolute values for 24 Hz being 101.4 +/- 11.7 cmH2O for PVL (n = 8) and 86.4 +/- 11.4 cmH2O for CON (n = 7) (NS). NO formation inhibition reversed the hyposensitivity in preparations of PVL, Hz50 being 13.9 +/- 0.5 and 13.2 +/- 0.2 for PVL and CON respectively (NS). Adrenergic receptor antagonism with prazosin (10(-7) mol L-1) and yohimbine (10(-6) mol L-1) inhibited PNS-mediated vasopressor reactivity (n = 6 per group, P < 0.001), confirming the nervous origin of vasoconstrictor responses. It is concluded that (1) portal hypertension goes along with a significant hyposensitivity to PNS and (2) this hyposensitivity is reversed by NO-formation inhibition
Subject(s)
Hypertension, Portal/physiopathology , Nitric Oxide/physiology , Peripheral Nerves/physiology , Animals , Electric Stimulation , Male , Nitroarginine/pharmacology , Prazosin/pharmacology , Rats , Rats, Sprague-Dawley , Vasoconstriction/drug effectsABSTRACT
Process development for the production of a therapeutic humanised antibody is a very complex operation. It involves recombinant genetics, verification of a strong expression system, gene amplification, characterisation of a stable host cell expression system, optimisation and design of the mammalian cell culture fermentation system and development of an efficient recovery process resulting in high yields and product quality. Rapid progress in the field and the wish of some pharmaceutical companies for outsourcing their production are the driving forces for process changes relatively late in the development phase. This literature survey is aimed at identifying the limits of acceptable process changes in up scaling of the fermentation and down stream processing of biopharmaceuticals and defining the demand in production validation to prove product equivalency and identity of the isolated, purified therapeutic antibody.
