Franco Bacciottini

Polyamine distribution and activity of their biosynthetic enzymes in the European sea bass (Dicentrarchus labrax L.) compared to the rat

1. In the liver, heart and brain of the European sea bass, putrescine concentrations are much higher than in the equivalent rat tissues; spermidine and spermine levels are smaller. 2. Ornithine decarboxylase in the bass liver is more active, but less stable than that in the rat; stability is acquired upon partial purification. Bass liver adenosylmethionine decarboxylase activity is less than that found in the rat. Both are activated and stabilized by putrescine. 4. The activating effect of putrescine decreases as the assay temperature is decreased. This may explain the high level of putrescine but low levels of spermidine and spermine in the bass liver.

A possible role for polyamines in cartilage in the mechanism of calcification

The role of polyamines in cartilage is not known: they may be somehow related to the mechanism of calcification. In epiphyseal cartilage from calf scapulas, they are more concentrated in the ossifying area, where calcification takes place, than in the resting region. Spermidine is present in greater amounts than spermine and putrescine. Since ornithine decarboxylase (EC 4.1.1.17) is measurable only in the resting region of the tissue, it is in this area that polyamine biosynthesis occurs, while they accumulate in the ossifying area. Immunohistochemical evidence is obtained that only in the ossifying zone is spermidine extracellular. It is at this level that the matrix is rearranged to become calcified, and proteoglycans are dissociated and partially removed. The effect of polyamines on solutions of proteoglycan subunits has been studied in vitro by following variations of turbidity and viscosity. While in the presence of putrescine the specific viscosity decreases to asymptotic values, in the presence of either 30 mM spermidine or 2.5-10 mM spermine, the decrement is more marked. At the same concentrations, increase of the turbidity of proteoglycan subunit solutions was observed. Only spermidine showed the capacity of displacing proteoglycan subunits from a column of Sepharose 4B-type II collagen: at 15 mM concentration, about 90% of proteoglycans were removed from the column. Alkaline phosphatase activity, which plays an important role in calcification, is enhanced by spermidine and spermine. These results obtained in vitro support the hypothesis that polyamines may be related to calcification of preosseous cartilage.

Ornithine decarboxylase in perfused rat heart

In the isolated perfused rat hearts, the activity of tissue ornithine decarboxylase gradually decreases over 90 min. In contrast, the activity of S-adenosylmethionine decarboxylase, lactate dehydrogenase, and glutamate-oxalacetate transaminase stays unchanged after a small decrease during the first 10 min. Ornithine decarboxylase is released from the perfused heart under conditions in which neither the lower molecular weight S-adenosylmethionine decarboxylase nor polyamines leak out. Ten minutes of ischaemia did not change the rate of release of ornithine decarboxylase. Ischaemia followed by reperfusion (20 min) increased release of ornithine decarboxylase.

Effect of temperature and diet on polyamine concentrations of the European sea bass (Dicentrarchus labrax L.)

Abstract 1. 1. A fall of environmental temperature causes a decrease in total polyamine concentrations of heart, red and white muscles of sea bass fed on a diet containing 70% herring meal (diet S). 2. 2. When sea bass was fed with a diet partially replaced by casein (diet A), an increase of total polyamine concentration in liver and heart was observed at a lower temperature. 3. 3. In all tissues studied an increase of putrescine concentrations and a parallel decrease of spermidine and spermidine levels were found for both groups S and A of sea bass when the temperature was lowered. 4. 4. In general concentrations of putrescine, spermidine and spermine were considerably higher in group A when the temperature was lowered.