Ballard, Heather J.

Ballard, Heather J.

Associate Professor

e-mail: ballard@hkucc.hku.hk

Tel.: 2819-9232

Faculty Teaching Medal, HKU (2002)

Cardiovascular Physiology

My research is focused on the cardiovascular responses to hypoxia or exercise, particularly, the mechanisms that control the blood flow to skeletal muscle under these conditions.

The contributions of different metabolic substances to exercise hyperaemia in skeletal muscle have been investigated in recent years, and adenosine remains an important focus in our studies. Current work in this area addresses the mechanisms by which muscle pH and/or muscle contractions control the efflux of ATP from the muscle cell, which plays a major role in the control of extracellular adenosine formation.

The role of acute hypoxia (as distinct from ischaemia) in the metabolic control of blood flow is another major area of interest. We focus on the role of endothelium-derived factors, including adenosine, potassium, prostaglandins and nitric oxide, in the control of skeletal muscle blood flow, and the mechanisms by which the hypoxia gives rise to the formation / release of endothelial factors. Our present studies are directed towards identifying the site of the adenosine formation in skeletal muscle vascular endothelial cells, and quantifying the contribution of endothelially-derived adenosine to the overall vascular response.

Experimental approaches employed in my laboratory range from studies of integrated mammalian physiology down to single cell systems and enzyme studies in fractionated cells. Techniques include interstitial microdialysis, HPLC, spectrophotometric assays, various gas- or ion-sensitive electrodes, confocal microscopy and intracellular pH measurements using fluorescent dyes.

REPRESENTATIVE PUBLICATIONS

Mo, F.M and Ballard, H.J. (2005) Acute systemic hypoxia elevates venous but not interstitial potassium of dog skeletal muscle. Am. J. Physiol. Heart & Circ. 289, H1710-H1718.
Yeung, E.W., Balnave, C.D., Ballard, H.J., Bourreau, J-P and Allen, D.G. (2002) Development of T-tubular vacuoles in eccentrically-damaged mouse muscle fibres. J. Physiol. 540, 581-592.
Mo, F.M. and Ballard, H.J. (2001) The effect of systemic hypoxia on interstitial and blood adenosine, AMP, ADP and ATP in dog skeletal muscle. J. Physiol. 536, 593-60
Cheng, B., Essackjee, H.C. and Ballard, H.J. (2000) Evidence for control of adenosine metabolism in rat oxidative skeletal muscle by changes in pH. J. Physiol. 522, 467-477.
Mo, F.M. and Ballard, H.J. (2000) The effect of lactic acid on intracellular pH and adenosine output from superfused rat soleus muscle fibres. Life Sci. 67, 227-234.