Influences of dietary linoleic acid on coronary flow, left ventricular work, and prostaglandin synthesis in the isolated rat heart

Because of the frequent occurrence of ischemic heart disease, interest in the consequences of dietary fat intake for the heart has increased strongly. and many studies have shown the importance of dietary fat for the heart. Most studies deal with the role of dietary fat in coronary atherosclerosis and the incidence of ischemic or coronary heart disease due to the obstruction of the coronary arteries by atherosclerotic plaques. Several studies have shown that dietary fat can also affect the myocardial muscle cell directly. The best known and most extensive studies in this field are those of essential fatty acid deficienCy and dietary rapeseed oil containing a high amount of erucic acid. Onty few studies on the effects of other dietary fats on the heart. in which athAosclerosis is not involved. have appeared. However. the interest in direct effects of dietary fat on the heart is growing. The final objective of the present study is to gain information about possible favourable and unfavourable properties of dietary fats used for human consumption. The particular objectives of the study were to investigate influences of fats fed to rats for a short period of time on coronary flow rate and external left ventricular work in their isolated. perfused hearts. As the effects found could be ascribed to dietary linoleic acid. which is the ultimate precursor of the prostaglandins of the 1- and 2-series. it was investigated whether prostaglandin synthesis in the isolated heart waS involved. The build-up of the thesis is as follows. Chapter I gives a review of the effects of dietary fat on the heart (excluding atherosclerosis). as well as a review of the differences found in the heart in the oxidation rates and metabolism of various long-chain fatty acids. Chapter 2 contains methods and procedures and a discussion on the use of the isolated. working rat heart for physiological investigations. A discussion on expressing the heart function parameters used per unit of dry heart mass is given in chapter 3. The investigations into the effects of various dietary fats and of prostaglandins in the isolated heart are presented in chapters 4-6 and in the Addenda. Tbe overall discussion on the influences of the dietary fats used on coronary flow rate and external left ventricular work. and on the role of prostaglandins is given in chapter 7.