Oesophagostomum dentatum: population dynamics and synthesis of prostanoids by histotropic stages cultured in vitro.

The dynamics of production and excretion of prostanoids by histotropic larvae of Oesophagostomum dentatum and the role of prostanoids for the development of O. dentatum were studied under in vitro conditions. In control cultures fourth stage larvae (L4) were first seen on Day 7 of in vitro cultivation. Their numbers steadily increased until Day 21 of in vitro cultivation. Thereafter, the numbers of L4 no further increased. The continuous presence of inhibitors of prostanoid synthesis such as acetylsalicyclic acid (ASA, 5.6 mmole/liter) or indomethacin (INDO, 1.4 mmole/liter) in the culture medium blocked the development to L4 almost completely. When ASA was given first on Day 13 of in vitro cultivation L4 counts still increased during the following 4 days. However, the numbers of larvae which reached the L4 stage in these cultures was reduced to 65% of that in control cultures. Resumption of development to L4 was seen after the withdrawal of INDO in cultures treated with this drug until Day 13 of in vitro cultivation. Larvae and supernatants were collected separately on Days 7, 14, 21, or 28 of in vitro cultivation and larvae were homogenized. The presence of prostaglandin (PG) E2, PGD2, PGF2 alpha, 6-keto-PGF1 alpha, and thromboxane (TX) B2 was assayed radioimmunologically in homogenates and supernatants. In the homogenates only PGE2 and PGD2 were regularly detected. The total amount of PGE2 and PGD2 in the homogenates significantly increased with the increase in L4 numbers, whereas the homogenate protein-based values did not. In addition to PGD2 and PGE2, PGF2 alpha and TXB2 were found in the supernatants. PGE2 accounted for about 50% of the prostanoids in the supernatants on Day 7 of in vitro cultivation but was generally absent thereafter. After 14, 21, and 28 days of in vitro cultivation TXB2 was the most prominent single prostanoid in the supernatants. PGD2 was found in the supernatants only after 7 and 28 days of in vitro cultivation. PGF2 alpha was present in decreasing amounts in the supernatants throughout the cultivation period. In conclusion, histotropic larvae of O. dentatum produce and excrete mediators of the prostanoid type which may serve as endogenous hormone-like growth factors.