SEASONAL-VARIATIONS IN CYCLIC-GMP RESPONSE ON WHOLE-BODY COOLING IN WOMEN WITH PRIMARY RAYNAUDS-PHENOMENON

1. Primary Raynaud's phenomenon (PRP) is characterized by increased va soconstrictor tone that develops during exposure to cold. The symptoms are most pronounced during the winter months with low outdoor tempera ture, The L-arginine-nitric oxide (NO)-cyclic GMP (cGMP) pathway plays an important role in counteracting vasospasm. The aim of the present study was to investigate if the venous cGMP response to whole-body coo ling in women with PRP varied with the season of the year. 2. The stud y was performed as an open parallel-group comparison between women wit h PRP and healthy female controls during the winter months of February 1994 and 1995 and in the summer month of August 1994, Blood samples w ere drawn just before and 40 min after whole-body cooling. 3. There we re no significant changes in venous cGMP after whole-body cooling in w omen with PRP during the winter months of February 1994 and 1995, Cold exposure in the summer month of August resulted, however, in a signif icant increase in venous cGMP (P < 0.01). In contrast, the healthy wom en responded with a significant increase in venous cGMP on all three t est occasions: February 1994 (P < 0.05), August 1994 (P < 0.05) and Fe bruary 1995 (P < 0.01), 4. A seasonal variation in venous cGMP respons e to whole-body cooling was observed only in women with PRP Healthy wo men responded to cold exposure with an increase in venous cGMP during summer and winter, whereas females with PRP showed an increase only du ring summer. Results from the present study might indicate seasonal va riation in the regulation of constitutive nitric oxide synthetase in w omen with PRP, which may contribute to new therapeutic approaches.