EFFECT OF GAMMA-LINOLENIC ACID, DIHOMOGAMMALINOLENIC ACID, ASCORBYL-6-GAMMA-LINOLENIC ACID AND ASCORBYL-6-DIHOMO GAMMA-LINOLENIC ACID ON HISTAMINE-INDUCED AND METHACHOLINE-INDUCED CONTRACTION OF THE ISOLATED GUINEA-PIG TRACHEAL CHAIN
Cp. Kahler et Wj. Duplooy, EFFECT OF GAMMA-LINOLENIC ACID, DIHOMOGAMMALINOLENIC ACID, ASCORBYL-6-GAMMA-LINOLENIC ACID AND ASCORBYL-6-DIHOMO GAMMA-LINOLENIC ACID ON HISTAMINE-INDUCED AND METHACHOLINE-INDUCED CONTRACTION OF THE ISOLATED GUINEA-PIG TRACHEAL CHAIN, Prostaglandins, leukotrienes and essential fatty acids, 58(4), 1998, pp. 327-331
The relaxant effects of gammalinolenic acid (GLA) and dihomo gammalino
lenic acid (DGLA) were compared to the relaxant effect of arachidonic
acid (AA). The effect of the combination of ascorbate to form the nove
l drugs ascorbyl-6-gammalinolenic acid (ascorbyl-6-GLA) and ascorbyl-6
-dihomo gammalinolenic acid (ascorbyl-6-DGLA) were investigated and th
e role of the epithelial cells was determined. Salbutamol was used as
control. The isolated tracheas of six to eight guinea pigs were used i
n each experiment and suspended in organ baths filled with Krebs-Hense
leit solution and aerated with 95% O-2 and 5% CO2. The relaxant effect
s produced for histamine-contracted preparations were as follows: AA =
71.2 +/- 0.2%, GLA = 55.2 +/- 4.2%, DGLA = 69.8 +/- 3.9%, ascorbyl-6-
GLA = 26.2 +/- 5.1% and ascorbyl-6-DGLA = 54.5 +/- 2.4%. For methachol
ine-contracted preparations: AA = 46.6 +/- 3.2%, GLA = 55.0 +/- 9.5%,
DGLA = 61.8 +/- 2.7%, ascorbyl-6-GLA = 40.0 +/- 8.0% and ascorbyl-6-DG
LA = 88.0 +/- 15.3%. Ascorbyl-6-GLA and ascorbyl-6-DGLA had mainly a d
ecreased relaxant effect compared to GLA and DGLA, except ascorbyl-6-D
GLA after methacholine-induced contraction, which showed a significant
increased relaxant effect. The removal of the epithelium showed decre
ased relaxant effects for the drugs except AA, which showed increased
values after methacholine contraction. Histamine-contracted preparatio
ns showed Varied results. Ascorbyl-B-GLA showed an increased relaxant
effect, DGLA was unaffected with no additional effect, and AA, GLA and
ascorbyl-6-DGLA showed decreased relaxant effects. In conclusion, it
is clear that the contractant and the availability of epithelial cells
could ultimately determine the results, though the mechanism remains
very complex. The benefit of added ascorbate is still unclear and warr
ants more investigation.