Some Factors That Affect Calcium-Sensitivity in the Rat Tail Artery

Ugwu, Andrew Chukwuma (1987) Some Factors That Affect Calcium-Sensitivity in the Rat Tail Artery. PhD thesis, University of Glasgow.

Abstract

The calcium sensitivity of noradrenaline (NA) and potassium chloride (KCl)-induced contractions of vascular smooth muscle were investigated in calcium readdition experiments under different oxygen tensions and temperatures in the isolated perfused rat tail artery (male Wistar, 300-350g). We started by establishing the most favourable conditions for responses of the smooth muscle in the preparation, and making an extensive analysis of the influence of experimental conditions on the concentration-response relationship to NA and in some cases, to KCl. This was carried out on both the proximal and distal portions of the vessel, applying NA both intraluminally and extraluminally. Both portions showed similar characteristics and intraluminal administration of NA was more effective than the extraluminal administration. But this difference in potency was abolished when cocaine was included in the saline during the comparisons of the routes of administration of NA. Factors analysed (alone and in combination) included cocaine, propranolol, EDTA, extracellular and intracellular modification of pH, oxygen, [Ca2+]o (including the use of Ca2+ buffers). Following this the alpha-adrenoceptor population was analysed using selective antagonists (prazosin and rauwolscine) and Ca2+-entry was manipulated using nifedipine (blocker) and Bay K 8644 (facilitator). The calcium sensitivity of noradrenaline (NA) and potassium chloride (KCl)-induced contractions of vascular smooth muscle were investigated in calcium readdition experiments under different oxygen tensions and temperatures in the isolated perfused rat tail artery (male Wistar, 300-350g). We started by establishing the most favourable conditions for responses of the smooth muscle in the preparation, and making an extensive analysis of the influence of experimental conditions on the contraction-response relationship to NA and in some cases, to KCl. This was carried out on both the proximal and distal portions of the vessel, applying NA both intraluminally and extraluminally. Both portions showed similar characteristics and intraluminal administration of NA was more effective than the extraluminal administration. But this difference in potency was abolished when cocaine was included in the saline during the comparisons of the routes of administration of NA.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Physiology
• Date of Award: 1987
• Depositing User: Enlighten Team
• Unique ID: glathesis:1987-77548
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jan 2020 09:05
• Last Modified: 14 Jan 2020 09:05
• URI: https://theses.gla.ac.uk/id/eprint/77548