Lipids or fats are heterogenous group of complex molecules having high caloric value present in all biosystems. Lipids are generally stored in the liver, adipose tissue and muscles, and are one of the most important fish energy sources. They are mobilized when food intake cannot supply the energy demands of growth and maintenance. Lipase is a metabolic enzyme associated with the reactions of lipolysis and lipogenesis i.e. breakdown of lipids into fattyacids and glycerol resulting in the release of water and energy; and the synthesis of neutral lipids by its reverse reaction, respectively. In the present study fresh water fish Catla catla was exposd to lead and chromium heavy metals and study the total lipids and lipase activity in various tissues of the fish. Total lipids were decreased in all the tissues irrespective of the toxicant, where as there was a increase in the lipase activity under the influence of lead and decrease under the influenced of the chromium.
