Thesis (M.Sc.)--Chulalongkorn University, 1996

Examines the effects of garlic extract on coronary arteriolar responses to vasoactive agents in streptozotocin-induced diabetic rats (STZ-rats) at 8,12, and 16 weeks. The isolated arrested hearts were prepared to investigate responses of coronary arterioles (diameter 40-55 mum) to acetylcholine (Ach; 10-4 M), sodium nitroprusside (SNP; 10-4 M), norepinephrine (NE; 10-4 M) and indomethocin (Indo; 10-4 M). Changes in diameter to topical application of these agents were determined by using intravital fluorescence microscopy and digital image processing analysis. The results assessed by means percent changes of studied arteriolar diameter (%d) indicated that the impairment of coronary arteriolar responses to Ach and NE were significantly obtained in STZ-rats (n=6) as compared to their age-matched controls (n=6) (controls:% dAch=12.75 _+ 0.88 ;% dNE=12.44 _+ 1.83, STZ-rats : % dAch =6.55 _+ 1.41; % dNE =17.89 _+ 0.86). Interestingly, the results indicated that these abnormalities of arteriolar responses were attenuated by daily oral feeding of garlic extract (100 mg/kg bw/day). However, in the experiments using SNP found that there was no significant difference among those groups of controls (n=6), STZ-rats (n=6), and STZ-G-rats (n=6) (% dSNP = 15.24 _+ 1.12, 14.90 _+ 1.30 and 14.54 _+ 1.59 respectively). Interestingly, indomethacin produced vasoconstriction in controls (n=6) and STZ-G-rats (n=6) (control : % dIndo = 9.51 _+ 1.21, STZ-G-rats : %dindo = 7.84 _+ 0.77). But, it caused arteriolar dilation in STZ-rats (%dIndo = 7.06 _+ 1.29). Moreover, the results also demonstrated that garlic could attenuate the impairments of cardiac functions including systolic pressure, diastolic pressure, mean arterial pressure, heart rate, and aortic flow rate. It may conclude that the abnormalities of arteriolar responses to vasoactive agents have been observed in STZ-rats at 8, 12 and 16 weeks. And this derangement seems to be a type of endothelium-dependent. Interestingly, the daily oral feeding of garlic (100 mg/kg bw/day) could attenuate these abnormalities and also cardiac dysfunctions, therefore, garlic might be a great therapeutic tool in prevention of diabetic cardiovascular complications in the near future.