Prostaglandin synthesis by the lateral cochlear wall under streptomycin influence

Area of Science:

• Oto-pharmacology
• Biochemistry
• Cell Biology

Background:

• Prostaglandins (PGs) play crucial roles in cochlear physiology.
• Streptomycin, an aminoglycoside antibiotic, is known to cause ototoxicity.
• The effect of streptomycin on cochlear prostaglandin synthesis is not well understood.

Purpose of the Study:

• To investigate the impact of streptomycin on the synthesis of four key prostaglandins (PGD2, PGE2, PGF2 alpha, and PGI2) in the guinea pig lateral cochlear wall.
• To determine the influence of streptomycin dosage and duration of treatment on PG synthesis.

Main Methods:

• Guinea pigs were administered daily injections of streptomycin at varying dosages (20, 100, 200 mg/kg).
• Prostaglandin levels were measured using radioimmunoassay at 1, 5, and 10 days post-administration.
• Prostacyclin (PGI2) was detected as 6-keto PGF1 alpha.

Main Results:

• Streptomycin treatment led to a general reduction in PG synthesis, most pronounced for PGI2.
• PGI2 synthesis decreased to 50% at the lowest dose after 5 days and to 26% at the highest dose with prolonged treatment.
• PGE2 synthesis was also significantly reduced, following the decline in PGI2.
• The duration of streptomycin exposure appeared to have a greater impact on PG synthesis reduction than the dosage.

Conclusions:

• Streptomycin significantly inhibits prostaglandin synthesis in the guinea pig cochlea.
• The reduction in PG synthesis is likely due to the inhibition of cell membrane phospholipids, which are precursors to prostaglandins.
• These findings suggest a potential mechanism for streptomycin-induced ototoxicity involving altered cochlear biochemical pathways.