H. Okan KAMACI, Deniz Adnan ÇOBAN, Cüneyt SUZER, Bahadır AKSU, Şahin SAKA, Kürşat FIRAT

Exocrine Pancreas Development and Trypsin Expression in Cultured European Sea Bass (Dicentrarchus labrax) Larvae

Bu çalışmada açılımdan 40. güne kadar levrek (D. labrax) larvalarında ekzokrin pankreasın ontogenik gelişimi ve oluşum aşamaları incelenmiştir. Levrek larvalarında pankreasın fonksiyonel gelişimi tanımlamak için histolojik ve tripsinojen aktivitesinin incelendiği enzimatik teknikler kullanılmıştır. İlk pankreas oluşumu sindirim tüpünün dorsal bölgesinde tabakalaşmış olarak izlenmiştir. Eksokrin hücre farklılaşmasının ilk işaretinin kutuplaşma olduğu gözlenmiştir. 6. günde ilk zimojen granülleri ve ekzokrine polihedarl hücreli pankreas karaciğerin posteiorunda ve dorsal bölgesinde konumlanmış yoğun bir oluşum olarak gözlenmiştir. Aynı zamanda, ilk olarak anüs sonrasında ağız açılmış ve larvaların total boyu 3,47±0,26 mm olarak tespit edilmiştir. Larval metamorfoza kadar, pankreas farklılaşmış ve midenin mesenterik bölgesinde, bağırsağın ve pilorik çekumun üst kısmında yayılmış olarak izlenir. Öte yandan, zimojen granüllerinin sayısının ve hacminin artması ve beraberinde taşınan içerik miktarının artışı hücresel aktivitede meydana gelen artışın açık bir göstergesidir. Tripsin aktivitesi açılımın hemen ardından (42,54±6,8 mU/mg $protein^{-1}$) larva boyu ortalaması 4,28±0,2 mm iken tespit edilmiş ve özellikle eksojen besin alımının başlamasıyla birlikte sonraki günlerde düzenli artış göstermiştir. En yüksek tripsin aktivitesi 30. günde 122,45±11,76 mU/mg $protein^{-1}$ olarak tespit edilmiştir. Sonuçta, levrek larva üretim periyodunda eksokrin pankreas gelişimindeki en kritik aşamanın zimojen granüllerinin oluşumu olduğu ve tripsin aktivitesinin açılımın hemen ardından başlayıp larval gelişime bağlı olarak artmaya devam ettiği bulunmuştur.

Anahtar Kelimeler:

doku bilimi, levrek, ontogeni, büyüme, Dicentrarchus labrax, larva, tripsin

Kültürü yapılan Levrek (Dicentrarchus labrax) larvalarında ekzokrin pankreas gelişimi ve tripsin aktivitesi

The ontogenesis and formation stages of exocrine pancreas in European sea bass (D. labrax) larvae were investigated from hatching to 40 days after hatching (DAH). Histological and enzymatical techniques were used to explain the functional development of the pancreas in D. labrax with the expression of trypsinogen activity. The incipient pancreas appeared as a lamination of the dorsal wall of the digestive tract. It was observed that the primary visible indication of exocrine cell differentiation was polarization. The first zymogen granules and pancreas with exocrine polyhedral cells appeared on 6 DAH and became abundant as a compact structure located dorsal and slightly posterior to the liver. At the same time, firstly, anus and then mouth were opened, and total lengths of larvae were determined as 3.47±0.26 mm. Until larval metamorphosis, the pancreas became diffuse, spreading throughout the mesentery enclosure, the stomach, the upper intestine and the pyloric caeca. On the other hand, zymogen granules were more numerous and larger, and a greater quantity of material was carried by the ducts, indicating an increased cellular activity. The specific activity of trypsin was determined as early as after hatching (42.54±6.8 mU/mg $protein^{-1}$) at 4.28±0.2 mm total length of larvae and increased immediately during the following days especially after exogenous feeding. The highest tryptic activity was detected on 30 DAH as 122.45±11.76 mU/mg $protein^{-1}$. It is concluded that exocrine pancreas organogenesis is the main critical step of the zymogen granules and trypsin activity is present as early as after hatching and continuously increasing with larval period of D. labrax.

Keywords:

histology, sea bass, ontogeny, growth, Dicentrarchus labrax, larvae, trypsin,

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