Local control of the peripheral microcirculation in women: effects of the menstrual cycle and oral contraceptive use

Smart, Claire Louise (2005). Local control of the peripheral microcirculation in women: effects of the menstrual cycle and oral contraceptive use. University of Birmingham. Ph.D.

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Abstract

In women, levels of the hormones oestrogen and progesterone fluctuate endogenously during the menstrual cycle or exogenously during oral contraceptive (OC) use. Events surrounding menstruation have been described as having inflammatory elements. This thesis examines whether these events can modify peripheral vascular control with consequences for vascular permeability and fluid balance. It was shown that withdrawal of exogenous progesterone during transition from ‘high’ (late luteal) to ‘low’ (menstrual) hormone status in women using OC was not accompanied by changes in plasma levels of the chemoattractant IL-8, nor by a variation in circulating leucocyte counts. Accumulation of endometrial leucocytes prior to shedding may therefore be due to their proliferation in situ and/or localised chemoattraction balanced by increased white cell production. During the menstrual cycle, microvascular fluid filtration capacity, assessed in the lower leg by venous occlusion plethysmography, tended to be highest in the menstrual phase for non-OC and OC women, associated with the highest levels of urinary TNF-a. Decreases in calf blood flow in response to leg dependency (~ 30%) were independent of menstrual cycle phase or OC use, as were the effects of external compression, i.e. abolition of the vasoconstrictor response. Large increases in venous pressure are thought to evoke the anti-oedema veno-arteriolar vasoconstrictor response, while small cumulative pressure steps were expected to induce a flow-maintaining vasodilator response. The results presented suggest that the active mechanism in both protocols may simply be to maintain flow during increased venous pressure, and that veno-arteriolar vasoconstrictor mechanisms may only occur during limb dependency.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):