Front row duo sign new deals with Sarries
Loosehead Barrington, 26, has featured 82 times since joining Sarries from Jersey in 2013, and has agreed a three-year contract with the club.
Meanwhile, USA international Lamositele, 21, has signed a new two-year deal.
"Both Richard and Titi are valuable members of our squad," said Saracens Director of Rugby Mark McCall.
"Richard is blossoming into a fine prop forward since we signed him from the Championship, and he still has room for improvement, which is very exciting for both him, and the club.
"In terms of Titi, he has quickly established himself as an important member of our group, and to do so in such a short amount of time underlines his talent.”
Having shared the loosehead duties with Mako Vunipola and Rhys Gill in previous seasons, Barrington will have more responsibility within the Double Champions’ squad with Gill's move to Cardiff Blues over the off-season.
"I’m delighted to have signed a new contract, ever since I arrived at the club I've felt at home – so to have the chance to extend my stay at Allianz Park was an opportunity I jumped at," Barrington said.
"We have a great set of guys here, with an amazing coaching and backroom staff supporting us. I’m delighted to be staying."
Versatile prop forward Lamositele joins Barrington in signing a fresh deal with the club.
Lamositele, has 22 appearances for Sarries to his name.
"Saracens have been great with me and have really developed my game, it's such an exciting time to be associated with the club, and it's the perfect place for me to continue to learn my trade," Lamositele said.
"We have a great core of young players who will be at the club together for some time, so I'm really excited to be a part that."
