AJP - Heart and Circulatory Physiology, Vol 243, Issue 1 51-H60, Copyright © 1982 by American Physiological Society
Microvascular response to blockade of prostaglandin synthesis in rat skeletal muscle
J. E. Faber, P. D. Harris and I. G. Joshua
The contribution of endogenous prostaglandins (PGs) to the control of
arteriolar diameter in the microcirculation is incompletely defied and has
only been studied in drug-anesthetized animals. To test the possibility
that endogenous PGs are tonically released to exert a net dilator influence
at certain levels in the microcirculation, television microscopy was used
to quantitate the arteriolar responses in the rat cremaster muscle to local
blockade of PG synthesis with indomethacin. Rats were decerebrated by a
midcollicular transection and were allowed to recover from surgical
anesthesia. The cremaster muscle with intact circulation and innervation
was suspended by sutures in a temperature-controlled Krebs bath. Diameters,
vasomotion frequency, and vasomotion amplitude of arterioles at several
anatomic levels were measured before and after local inhibition of PG
synthesis in the presence and absence of alpha-adrenergic receptor
blockade. Inhibition of PG synthesis produced marked constriction (42-66%
of control) at all arteriolar levels, with greater responses occurring in
the smaller arterioles. PG synthesis blockade increased vasomotion
frequency in arterioles that exhibited spontaneous vasomotion during
control periods, and blockade induced vasomotion in vessels lacking
spontaneous vasomotion. Pretreatment with phentolamine significantly
attenuated the constriction and augmentation of vasomotion. These data
indicate that dilator PGs participate in the moment-to-moment regulation of
arteriolar tone and local blood flow in skeletal muscle. Further, their
mechanism of action may involve alterations in neuronal norepinephrine
release or alpha-receptor sensitivity.
